Basics of Clinical optics ophthalmic Instruments and

eye examinationDr Zia-Ul-Mazhry

FCPS(Pak) FRCS(Edin)

FRCS(Glasgow) CIC Ophth- (UK)

Associate ProfessorHead of Eye Department

Central Park Medical College amp WAPDA Teaching Hospital Complex Lahore

Pakistan

bull For Education purpose Onlybull Material Taken from Various Internet

Resources

Overviewbull Part 1

ndash Pretestbull Part 2

ndash Clinical Optics and their ophthalmic Significance

bull Part 3ndash Ophthalmic instruments and Dark Room Tests

in Ophthalmologybull Part 4

ndash Post Test

Objectives

bull The students should be able tondash Their learning needs and gainsndash Understand Clinical Optics and their

ophthalmic Significancendash Use Ophthalmic instrument and perform

eye Examination ndash Put it al together to Evaluate diagnose and

investigate common ocular conditions

Part 1

Pretest

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull For Education purpose Onlybull Material Taken from Various Internet

Resources

Overviewbull Part 1

ndash Pretestbull Part 2

ndash Clinical Optics and their ophthalmic Significance

bull Part 3ndash Ophthalmic instruments and Dark Room Tests

in Ophthalmologybull Part 4

ndash Post Test

Objectives

bull The students should be able tondash Their learning needs and gainsndash Understand Clinical Optics and their

ophthalmic Significancendash Use Ophthalmic instrument and perform

eye Examination ndash Put it al together to Evaluate diagnose and

investigate common ocular conditions

Part 1

Pretest

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Overviewbull Part 1

ndash Pretestbull Part 2

ndash Clinical Optics and their ophthalmic Significance

bull Part 3ndash Ophthalmic instruments and Dark Room Tests

in Ophthalmologybull Part 4

ndash Post Test

Objectives

bull The students should be able tondash Their learning needs and gainsndash Understand Clinical Optics and their

ophthalmic Significancendash Use Ophthalmic instrument and perform

eye Examination ndash Put it al together to Evaluate diagnose and

investigate common ocular conditions

Part 1

Pretest

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Objectives

bull The students should be able tondash Their learning needs and gainsndash Understand Clinical Optics and their

ophthalmic Significancendash Use Ophthalmic instrument and perform

eye Examination ndash Put it al together to Evaluate diagnose and

investigate common ocular conditions

Part 1

Pretest

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Part 1

Pretest

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Part 2Clinical Optics and their ophthalmic Significance

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Clinical Optics and their ophthalmic Significance

bull Language of Opticsbull Vergencebull Reflection and Refractionbull Lenses Mirrors prisms and fiber opticsbull Focal Length and focal power

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Language of Optics

bull Light and Light rays

bull Vergence

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Language of Optics

bull Object and Image

O

I

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Language of Optics

bull Lateral Reversal of Image

AMBULANCE

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Real vs Virtual Images

bull Real images are formed by mirrors or lenses when light rays actually converge and pass through the image

bull A real image can be projected onto a piece of paper or a screen If photographic film were placed here a photo could be created

bull Virtual images occur where light rays only appear to have originated

bull Virtual images canrsquot be projected on paper screens or film since the light rays do not really converge there

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Language of Optics

bull Medium and interface

Air

Water

Interface

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Language of Opticsbull Focal Length and Dioptric Power The degree of convergence or divergence of a lens is expressed in

terms of its powerThus power of a lens is defined as the reciprocal of its focal length

D = 100 f(cm)

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Lenses Focal Length

bull Like mirrors lenses have a principal axis perpendicular to their surface and passing through their midpoint bull Lenses also have a vertical axis or principal plane through their middle

bull They have a focal point F and the focal length is the distance from the vertical axis to F bull There is no real center of curvature so 2F is used to denote twice the focal length

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Language of Optics

bull Erect vs Inverted Image

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Language of Optics Simplified Ray Diagram

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Reflection of Light

bull A ray of light the incident ray travels in a medium

bull When it encounters a boundary with a second medium part of the incident ray is reflected back into the first medium

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Reflection

surface normalsameangleincident ray exit ray

reflected ray

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Diffuse reflection is reflection from a rough surface

Specular reflection is reflection from a smooth surface

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Plane Mirror

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Critical angle is the angle of incidence for which the angle of refraction becomes 90

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than the critical angle

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Mirage Pictures

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Mirages

Mirages are caused by the refracting properties of a non-uniform atmosphere

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

The incident angle of light reflected from the anterior chamber angle is greater than the critical angle at the corneandashair interface

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Fiber Optics

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Prisms

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Dispersion of LightDispersion is the separation of light into a spectrum by refraction This effect causes white light to split into it spectrum of colors

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

One of the most common of these is the rainbow which is caused by water droplets dispersing sunlight

Dispersion-Rainbows

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

REFRACTIONbull Refraction is the change in direction of a wave

due to a change in its optical medium

Normal

Lighter Medium

Denser Medium

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Reflection and Refraction

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

REFRACTION IN OPHTHALMOLOGY

bull The refraction test is an eye exam that measures a persons prescription for eyeglasses or contact lenses

bull This test is performed by an ophthalmologist or optometrist

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Lenses and Mirrors

Lensesbull A piece of glass

material used to converge or diverge transmitted light and form optical images

Mirrorsbull A surface that

reflects light without diffusion

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Concave and Convex Mirrors

Concave mirrors reflect light from their inner surface like the inside of a spoon

bull Convex mirrors reflect light from their outer surface like the outside of a spoon

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Convex Mirrors

bull Curves outwardbull Reduces imagesbull Virtual images

ndash Use Rear view mirrors store securityhellip

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Lens

bull A transparent material that is has at least one curved side

bull Refracts light in a predictable and useful way

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Types of Lenses

Converging Lensbull makes parallel light rays

come together bull Also known as convex

lensbull Thicker at the center

thinner at the edges

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Types of Lenses

Diverging Lensbull makes parallel light rays

move apartbull Also known as concave

lensbull Thinner in the center

thicker at the edges

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Lens Functionbull Change the appearance of

objects (image appears larger smaller upside down or misshapen)

bull Magnify imagesbull Project images onto a

screen

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Terminologybull Optical Centre (O) ndash centre of the lens also the

point where the principal axis crossesbull Axis of Symmetry ndash an imaginary vertical line

drawn through the optical center of a lens perpendicular to principal axis

Optical Centre (O)

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Focal Point

bull Since lenses have 2 sides they have a focal point on each side

bull The principal focus is where the light rays convergebull A converging and diverging mirror has the principal

focus on different sides of the lens

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Focal Point ndash Converging Lens

bull Principal focus is on the opposite side of the lens as the incident rays

Principal FocusSecondary Principal Focus

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Focal Point ndash Diverging Lens

bull Principal focus is on the same side of the lens as the incident rays

bull The focal point is virtual

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Focal Length

bull Focal length (f) is the distance between the principal focus and optical centre

bull Distance from F to O F to 2F Frsquo to O Frsquo to 2F are all equal

bull 2F and 2Frsquo are twice the distance away from the optical centre than the focus points

FFrsquo 2F2Frsquo O

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

TerminologyPrincipal Focus (F)bull A point on the principal axis where the light rays that are traveling

parallel to the principal axis appear to convergebull In a converging lens it is on the opposite side as the incident raysbull In a diverging lens it on the same side as the incident rays

Secondary Principal Focus (Frsquo)bull Focus that is on the opposite side as the principal focus located the

same distance from the lens as Fbull In a converging lens it is on the same side as the incident raysbull In a diverging lens it is on the opposite side as the incident rays

Focal Length (f)bull distance from the principal focus to the axis of symmetrybull Focal length is the same distance with the secondary principal focus

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Converging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FFrsquo

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Converging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Converging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FFrsquo

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A CONVERGING LENS

bull What happens when object is at Frsquo

2Frsquo 2Frsquo

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A CONVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 2 ndash travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A CONVERGING LENS

Ray 3 (optional since you only need 2 lines to form an intersection) ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A CONVERGING LENS

Draw the image given the point of intersection

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A CONVERGING LENS

5 Scenarios for the Object1 Beyond 2Frsquo Object is greater than 2 focal

lengths from the lens (dogt2f)2 At 2Frsquo Object is at 2 focal lengths (do=2f)3 Between 2Frsquo and Frsquo Object is between 1

and 2 focal lengths from the lens (fltdolt2f)4 At Frsquo Object is at the focal point (do=f)5 Between Frsquo and lens Object is less than 1

focal length away from the lens (0ltdoltf)

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Case 1 ndash Object beyond 2Frsquo

Size Attitude Location Type

Reduced Inverted Between F and 2F Real

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Converging LensObject beyond 2Frsquo

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Case 2 ndash Object at 2Frsquo

Size Attitude Location Type

Same size Inverted At 2F Real

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Size Attitude Location Type

Case 3 ndash Object between 2Frsquo and Frsquo

Enlarged

Inverted Beyond 2F Real

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Size Attitude Location Type

Case 4 ndash Object at Frsquo

No Image Formed

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Size Attitude Location Type

Case 5 ndash Object between Frsquo and lens

Enlarged

Upright Same side as object

Virtual

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Converging LensObject between Frsquo and Lens

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

CONVERGING LENSESThe first lens known to be used was a converging lens called a reading stone Reading stones formed images that were upright and larger than the object

How can a converging lens produce both upright and inverted images

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

DIVERGING LENSES

bull The focal point is virtualbull Thus the principal focus is on the same side

of the lens as the incident rays

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Diverging Lens

1 A light ray parallel to the principal axis will refract through the principal focus (F)

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Diverging Lens

2 A light ray passing through the secondary principal focus (Frsquo) will refract parallel to the principal axis

FrsquoF 2Frsquo2F O

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Light Rays with a Diverging Lens

3 A light ray through the optical centre (O) will keep travelling in the same direction without being refracted

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A DIVERGING LENS

1 Pick a point on the object (usually the top of the object)

2 Send any two light rays off the point on the object

3 Determine the refracted rays Light rays only refract when it hits the lens

4 Find the intersection of the light rays If the rays do not intersection extend the refracted ray until they do (exception donrsquot do this for parallel light rays)

5 Use the point of intersection to location off an object is needed to locate its image

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A DIVERGING LENS

bull Q Draw the ray diagram for this pencil to locate its image

FrsquoF 2Frsquo2F O

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 1 ndash travels parallel to the principal axis and is refracted through the principal focus (F)

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 2 ndash travels through the secondary principal focus (Frsquo) and refracts parallel to the principal axis

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Ray 3 (optional since you only need 2 lines to form an intersection)

travels through the optical centre (O) and continues straight without being refracted

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

LOCATING AN IMAGE ON A DIVERGING LENS

FrsquoF 2Frsquo2F O

Size Attitude Location Type

Reduced Upright Same side as object

Virtual

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Diverging Lens

The image formed is always virtual upright and smaller

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Concave Lens Ray Diagrams

Ray 1 - travels from the tip of the object parallel to the principal axis When it emerges from the lens it appears to come from the principal focus (F)

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Concave Lens Ray Diagrams

Ray 2 - travels from the tip of the object through the optical centre of the lens and is not refracted

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Concave Lens Ray Diagrams

The image occurs where these rays appear to intersect

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Part 3Ophthalmic instrument

and Examination Methods

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Dark room Tests

bull Oblique IlluminationDiffuse light examinationInspection

bull Distant Direct Ophthalmoscopybull Direct Ophthalmoscopybull Retinoscopybull Indirect Ophthalmoscopy

ndash Indirect Ophthalmoscopendash Slit Lamp Biomicroscopy

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Oblique IlluminationDiffuse light examination

bull Objectivendash Examination of External and anterior

Segment structuresbull Instruments

ndash Illumination Beamndash Magnification AidMicroscope

bull Methodndash Illumination beam at 45 degrees

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Slit Lamp

bull The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

SLEbull Observation by optical sectionbull Direct diffuse illuminationbull Indirect illuminationbull Retro-illuminationbull Scattering sclero-corneal

illuminationbull Fundus observation and

gonioscopy with the slit lamp

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Distant Direct Ophthalmoscopy

bull Objectivendash To Examine and classify media

opacities against fundal glowbull Instrumentation

ndash Direct Ophthalmoscopebull Methods

ndash Throw the light with DO at half meter 25-50 cm distance

ndash Parallax Method of deviation

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Distant Direct Ophthalmoscopy

bull Parallax Method of deviationndash Ask the patient to move hisher eyendash Opacities Moving

bull Withndash Anterior to nodal point

bull No movementndash At or very near to nodal point

bull Against Movementndash Behind the nodal point

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Distant Direct Ophthalmoscopy

bull Viewing ocular media ndash Observe red reflexndash Look for media

opacitiesbull Cataractsbull Corneal scarsbull Large floaters

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Direct Ophthalmoscopy

bull Objectivendash To examine the retinafundus

bull Instrumentationsndash Direct ophthalmoacope

bull Principle

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Principle of Direct Ophthalmoscopy

bull If patient and observer are both emmetropic rays emanating from a point in the patients fundus will emerge as a parallel beam and will be focused on the observers retina

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Fundoscopybull Fundoscopy is the

assessment of the fundus using an ophthalmoscope

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Examination Techniquebull dim the lightsbull ask the patient

to fixate on a distant target

bull approach the patient from the side

bull examine the optic nerve and surrounding retina

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Direct Ophthalmoscopy Basic skills

bull Proper position for central fundus viewing

bull Right eye to right eye bull Left eye to left eyebull Donrsquot rub noseshellip

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Direct Ophthalmoscopy Basic skills

bull Proper position for peripheral fundus viewing

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Direct Ophthalmoscopy Exam technique

bull Be systematicbull Start at optic disc amp work radiallybull Observe

ndash Optic disc CD rationdash Vessels course amp caliber AV ratio light

reflex crossingsbankingndash Maculandash Peripheral fundus

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Fundoscopy-Video

>

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Indirect Ophthalmoscopy

bull Objectivendash Fundus Examination

bull Instrumentationndash Indirect Ophthalmoscopendash Condensing Lens

bull Methods

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Funduscopy Techniquesinstruments

bull Direct Ophthalmoscopybull Indirect Ophthalmoscopybull Fundus Biomicroscopybull Fundus Contact Lens

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Why do we dilate pupils

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Direct Ophthalmoscopybull Advantages

ndash Portablendash Easy to usendash Upright imagendash Magnification 15xndash Can use wo dilation

bull Disadvantagesndash Small field of viewndash Lack of stereopsisndash Media opacities can degrade

image

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Indirect Ophthalmoscopybull Monocular or binocularbull Advantages

ndash Wide field of viewndash Binocular instruments

provide stereopsisbull Disadvantages

ndash Requires more skillndash Decreased magnification

(3x)ndash Requires dilationndash Inverted image

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Indirect Ophthalmoscopy principle

bull The principle of indirect ophthalmoscopy is to make

bull the eye myopic by placing a strong convex lens in front

bull of it This forms a real inverted image of the fundus in

bull the air between the lens and the observer

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Fig 5 Limited field of view in the direct method Peripheral pencils of light do not reach the observers pupil

Fig 6 Extended field of view in the indirect method The ophthalmoscopy lens redirects peripheral pencils of light toward the observer

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Indirect Ophthalmoscopy

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Fundus Biomicroscopybull Field of View amp Mag

ndash FOV ltindirect but gtdirect

ndash varies wlens amp slit lamp mag

bull Inverted imagebull Stereopsisbull Dilated pupilbull Requires skill

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Fundus Biomicroscopy

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Fundus Contact Lensbull Requires physical

contact weyebull Viewed

wBiomicroscopebull Advanced dx amp

surgerybull Field of view amp Mag

vary wlens design

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Normal Fundus

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Viewing the Optic Nerve Head

bull Observendash Sizendash Shapendash Colorndash Marginsndash Cup to disc ratio (CD) horiz amp Vert

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Blood Vessel Evaluation

bull Observendash Vessel diameterndash Shapetortuosityndash Colorndash Crossingsndash Light reflexndash ArteryVein (AV) ratio after 2nd

bifurcation

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Retinoscopy

bull Objectivendash To determine refractve status of the eye

bull Instrumentationndash Retinoscopendash Trial Lens setndash Trial frame

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Retinoscopy

bull Methodsndash Ask the patient to fixate on a distant targetndash Half to 1 meter distancendash Project the streak on pupilndash Move the streak and observe the movement

of red reflex

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

RetinoscopybullMoves with

ndashEmetropiandashHyperopiandashMyopia of less than 1 diopter

bullNo MovementndashMyopia of exactly 1 diaopter

bullMoves againstndashMyopia of more than 1 diopter

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Retinoscopy

bull Insert +1 D Lens in front of the eye while working at 1 meterndash No movement

bull Emetropiandash With movement

bull Hyperopiandash Against movement

bull Myopia of lt 1 D

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Retinoscope

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

RETINOSCOPE

BASIC CONCEPT

1) EMMETROPIAbull Light emerge Parallel

2) HYPEROPIAbull Light emerge Diverge

3) MYOPIAbull Light emerge Converge

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

EMMETROPIA

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

RETINOSCOPE

HYPEROPIA

Diverge

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MYOPIA

converge

RETINOSCOPY

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull BREAK PHENOMENONIris pupil Streak light light

reflex

No Break Break

RETINOSCOPY

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull THICKNESS PHENOMENON

Same thickness Different thickness

RETINOSCOPY

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull SKEW PHENOMENONlight reflex movement streak movement

No skewness Skew

RETINOSCOPY

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull MOVEMENT PHENOMENON

With movement Against movement

RETINOSCOPY

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull NEUTRALITY

- pupil fills- no movement

RETINOSCOPY

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull With movementsndash Hyperopendash Neutralize with Plus lenses (convex lenses)

bull Against movementsndash Myopendash Neutralize with Negative lenses (concave

lenses)

RETINOSCOPY

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull Working Distance Lensesndash Purpose Light emerge from Pt eye

conjugate with examinerrsquos retinabull +150 D - 667cmbull +200 D - 500cm

RETINOSCOPY

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Retinoscopy Video

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

The Reflection

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

Part 6

Post Test

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-1

bull The Focal length of a lens is

a) Inversely proportional to radius of the lens

b) Directly proportional to the power in diopter

c) Inversely proportional to power in diopter

d) Is not related to power to diopter

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-2

bull Average dioptric power of adult cornea is

a) 32 Db) 42 Dc) 52 Dd) 62 D

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-3

bull Average axial length of the normal adult eye is

a 18-20 mmb 12-14 mmc 16-18 mmd 22-24 mm

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-4

bull Clinical assessment of cataract progression is done through

a Snellenrsquos visual acuity testb Distant Direct ophthalmoscopyc Slit lamp Examinationd all of above

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-5

bull A perimetry is used to measure

a Central and peripheral fieldsb Visual acuityc Intra ocular pressured Central field only

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-6

bull Objective of distant direct ophthalmoscopy is

a Scleral examinationb Conjunctival examinationc Examination of media opacitiesd Fundus examination

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-7

bull The image formed during direct ophthalmoscopy is

a Inverted and realb Erect and realc Inverted and virtuald Erect and virtual

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-8

bull In the process of reflection Angle of incidence is always

a Equal to angle of reflectionb Grater than angle of reflectionc Lesser than angle of reflectiond None of above

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-9

bull Most of the refraction occurs at the site of

a Retinab corneac Lensd Aqueous humor

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

MCQ-10

bull Test being performed is used to measure

a Corneal diameterb Lens Thicknessc Anterior chamber Angled All of above

bull Thank youbull wwweyeacuitycombull wwwslidesharenet

bull Thank youbull wwweyeacuitycombull wwwslidesharenet