Retinoscopy

Michael Davidson

and

Paul Miller

Retinoscopy: Research Applications

• Normal refractive state and prevalence of refractive error in dogs, cats, horses, rats, raptors, gorilla, ostrich, elephant. Numerous studies.

• Myopia and ammetropia in dog breeds, guide dogs. Murphy CL et al. Invest Ophthalmol Vis Sci 1992; 33: 2459-63.

• Refractive state of aphakic/pseudophakic dogs, modal IOL strength. Davidson MG et al. Am J Vet Res 1993; 54; 174-7.

• Modal IOL strength in cats. Gilger BC et al. Am J Vet Res 1998; 59: 1339-43.

• Naturally occurring canine models of myopia. Kubai MA et al. Invest Ophthal Vis Sci2013; 54: 7324-8; Williams LA et al. Optom Vis Sci 2011; 88: 269-74; Black J. et al. Invest Ophthalmol Vis Sci 2008; 49: 4784-9; Mutti DO et al. Invest Ophthalmol Vis Sci 1999; 40: 1577084.

• Refractive state with foldable IOLs in dogs. Gaiddon JA et al. J Am Vet Med Assoc2000; 216: 864-9.

• Refractive state in cats with aqueous humor misdirection syndrome. CzederpiltzJM et al. J Am Vet Med Assoc 2005; 227: 1434-41.

Retinoscopy: Research Applications • Breed-related trends in ammetropia. Kubai MA et al. Am J Vet Res 2008; 69: 946-51.

• Refractive state with different IOL designs in dogs. Gift BW et al. Vet Ophthalmol 2009; 12: 13-21.

• “Modal” IOL dioptric power in horses. McMullen RJ et al. Am J Vet Res 2010; 71: 809-16.

• Refractive state after vitreoretinal surgery in dogs. Hoffman A et al. Am J Vet Res 2012; 73: 1299-304.

• Validation of handheld autorefractor in dogs. Groth A et al. Vet Ophthalmol 2012: 16: 319-323

• Effect of tropicamide on refractive state and aberrant retinoscopic reflexs in horses. McMullen RJ et al. Vet Ophthalmol 2014; 7: 120-5.

• Calculation of modal IOL in rabbits. Sanchez RF et al. Vet Ophthalmol 2016; 20: 242-249.

• Effect of refractive error on VEPs in dogs. Ito Y et al. J Vet Med Sci 2016; 78: 505-508.

Refractive Errors are Clinically Relevant• Refractive error induced with lens removal, vitreoretinal surgery, corneal surgery

• 15% of German Shepherd guide dogs vs. 53% of pet German Shepherd dogs are myopic from selective training (Murphy CL et al. Invest Ophthalmol Vis Sci 1992; 33: 2459-63).

• 32% of 1440 dogs surveyed had refractive error >0.5 diopters, specific breeds had higher incidence of ametropia (Kubai et. al. Am J Vet Res, 2008, 69:946-951)

• Myopia in Labrador Retriever and English Springer spaniel has heritable basis (Black et al. Invest Ophthalmol Vis Sci.2008;49:4784-4789; Kubai et. al. Invest Ophthalmol Vis Sci 2013;54:7324-8).

• Visual acuity in dogs decreases by 60% for every 1 diopter optical defocusing (Murphy et al. Am J Vet Res 1997. 58:414-418.)

• Optical defocusing of 1.5-3.0 diopter significantly increases retrieval time in field trial dogs (Ofri et al. Am J Vet Res 2012:73:546-50)

• Border Collies in sports performance disciplines who had training issues had a higher prevalence of refractive errors than those without training issues (Tomkowicz et al, ECVO abstract, 2018)

Training or Performance Issues

• Refractive error often not at fault, but retinoscopy allows the clinician to rule this out as a contributing factor.

Basic Definitions of Refraction and Refractive Properties

• Vergence - The character of light rays, defined as positive (convergent), negative (divergent), or plano (parallel) vergence.

• Refraction - Bending of light rays with a lens system. Plus lenses (convex) converge light rays while minus lens (concave) diverge light rays.

• Diopter (D) – A measure of lens power, defined by its focal point in meters (i.e., 5 diopter lens has a focal point of 0.2 meters or 1meter/5D).

• Optical Infinity – Any distance greater than 6 meters.

www.cybersight.org

Basic Definitions of Refraction and Refractive Properties

• Meridian - An imaginary line on the surface of a spherical body, for example on the cornea (for example, horizontal and vertical meridians).

www.helio.com

www.cybersight.org

Basic Definitions of Refraction and Refractive Properties• Emmetropia - An eye without refractive error

where the plus lens of the cornea and crystalline lenses refract light to a point source on the retina.

• Ametropia - An eye with a refractive error, generally from variations in the axial length of the eye, astigmatisms, or a shift in position or absence of the lens.

• Myopia – (Nearsightedness) An eye with a refractive error caused by relatively too great a refractive power, generally caused by a longer than normal axial length.

• Hyperopia – (Farsightedness) An eye with a refractive error caused by relatively too little refractive power, generally caused by a shorter than normal axial length.

• Anisometropia - Difference in refractive state of the two eyes.

www.patient.info

Basic Definitions of Refraction and Refractive Properties

• Astigmatism - an aspherical refractive error, caused when the refractive surfaces of the eye have different radii of curvature in different meridians (generally in the cornea). Such an eye has two or more points of focus on incident light rays. www.eyeglassguide.com

www.simplyoptometry.com

Principles of Retinoscopy or

“Putting Yourself at the Far Point of the Patient’s Eye”

Retinoscopy (Skiascopy)

• objective means of determining refractive or dioptric state of the eye

• observing reflected light rays or “reflexes” in the pupil created by illuminating the retina with a band (streak) of light from a retinoscope

• the character of the ”reflexes”, and how they are influenced by refractive lenses placed in the light path indicates refractive power of the eye

Design of Retinoscope(A retinoscope is not a direct ophthalmoscope)

• light projection system:

•bulb filament emits a streak of light•condensing lens•mirror

Design of Retinoscope

• light projection system:• sleeve controls vergence

and orientation of the light streak

Design of Retinoscope• light projection system:

• raising and lowering sleeve controls beam vergence

• rotating sleeve controls orientation of the light streak

Design of Retinoscope:Light Projection System

Design of Retinoscope

• examiner observation system:

• peephole aperture allows examiner to view emergent (reflected) light rays from the eye

Retinoscopes

Welch Allyn Hiene

Refracting Lens

•Lens bar or rack:• Series of spherical plus and

minus lenses in increments of 0.5D to 1.0D

• Generally, black bar contains plus lenses, red bar minus lenses, some designs may be the opposite.

Luneau Lens BarsHelpful tip….the black bars have a small convex bubble on the handle, the red bars a concave bubble, that allow identification “by feel” in the dark

DISCLAIMER

•The next series of slides explains the optics of retinoscopy.

• It is not necessary to fully understand the optics of retinoscopy to accurately perform retinoscopy.

•So……if you don’t understand everything, you will still be able to perform retinoscopy…..however, understanding the optics will broaden your mind, enrich your life, and impress your friends and mentors.

Incident (Incoming) Light Rays and Refractive State

• incident light rays acted on by lens systems of the eye

• emmetropic eye:• focal point on retina

• hyperopic eye:• focused beyond retina

• myopic eye:• focused in front of

retina (in vitreous)www.patient.info

Retinoscopic Reflexes

• emergent light rays reflecting from the retina leave the eye and are refracted by the lens systems of the eye in the same manner as incident light rays

• emmetropia:

• leave eye as parallel rays

• hyperopia:

• leave eye as diverging rays

• myopia:

• leave eye as converging rays

Image formation

Retinoscopy

Far Point of the Eye• point in space, conjugate with, or

corresponding to, the retina

• emmetropic eye:

• emergent light as parallel rays; far point AT infinity (>6 meters)

• hyperopic eye:

• emergent light as divergent rays; far point BEYOND infinity

• myopic eye:

• emergent light as convergent rays; far point IN FRONT OF infinity

Emergent Light Rays Viewed with Retinoscope

• appear as band of light, in the pupil, with adjacent shadow as streak is passed across patient’s pupil

Infinity – or 6m

“Face band” or “intercept”

Retinoscopic“reflex”

Emergent Light Rays Viewed with Retinoscope

•“With” Motion

•“Against” Motion

•Neutralization

Retinoscopy Reflexes Viewed at Optical Infinity

• Light rays reflected from the retina that are parallel (emmetropia) or divergent (hyperopia) have a far point at infinity or beyond infinity, respectively

• Light rays have not crossed – and produce a “with motion” • I.e. the streak in the pupil moves in the same direction of the sweep

Infinity – or 6m

Infinity – or 6m

EMMETROPIA

HYPEROPIA

Retinoscopy Simulator

• VIDEO

“With Motion”

Video courtesy of Dr. Paul Miller

Retinoscopy Reflexes Viewed at Optical Infinity

• Light rays projected from the retina that are converging (myopia) and have a far point in front of infinity

• Rays have converged and are inverted and reversed - and produce an

“against motion” • I.e. the streak in the pupil moves opposite the direction of the sweep

Infinity – or 6m

Myopia A

B

B

A

Retinoscopy Simulator

• VIDEO

“Against Motion”

Video courtesy of Dr. Paul Miller

Retinoscopic Reflexes-Neutralization

• If the emerging light rays are AT the far point of the eye, the pupil completely fills with light and no motion is seen as you sweep the streak across the pupil

Retinoscopy Simulator

• VIDEO

Neutralization

Video courtesy of Dr. Paul Miller

Against motion (2D), neutralization (1.5D) with motion (1.0D) Neutralization

Retinoscopic Reflexes

• If the far point of the eye is behind the point of observation (the retinoscope), A WITH MOTION is seen

• If the far point of the eye is in front of the point of observation, an AGAINST MOTION is seen

• If the far point is at the point of observation, NEUTRALIZATION IS SEEN

• The goal of retinoscopy is to find the far point!

Retinoscopy Working Distance

• optical infinity (>6meters) too distant from eye to perform retinoscopy

• infinity recreated by placing retinoscope at a known distance from eye (either 50cm or 66cm), i.e the “working distance” and placing a “working lens” in the path of reflected light rays

• the dioptric power of the working lens is subtracted from the gross refraction results to give a net or actual refraction

The Lenses – Neutralizing Lens

• The goal of retinoscopy is to find the far point of the eye (NEUTRALIZATION)

• A single lens is used to find NEUTRALIZATION that combines the working lens and any addition correcting lens

• Positive (black) lens converge light rays and “pulls” far point closer to the eye

• Negative (red) lens diverge light rays and “pushes” far point away from the eye

Finding the Far Point or Neutralization(THIS IS IMPORTANT)

• “with” motion wants PLUS lenses

•“against” motion wants MINUS lenses

Quiz 1

Q1: What retinoscopic reflex is seen if the far point of the patient’s eye is behind, in front of, and at the retinoscope?

A. With motion, against motion, neutralization, respectively

B. Against motion, with motion, neutralization, respectively

C. With motion, neutralization, against motion, respectively

D. Neutralization, against motion, with motion, respectively

Q2: What retinoscopic reflex is seen is the retinoscope is behind, in front of, and at the far point of the patient’s eye respectively?

A. With motion, against motion, neutralization respectively

B. Against motion, with motion, neutralization respectively

C. With motion, neutralization, against motion respectively

D. Neutralization, against motion, with motion respectively

Q3. The correct working distance for most individuals to perform retinoscopy is: A. 6 meters

B. 1 meter

C. 66cm

D. 33cm

Q4. What type of lens do you add in front of the patient’s eye if you see a with motion, against motion and neutralization?

A. Minus, plus and no lens respectively

B. Minus, no lens, and plus respectively

C. Plus, minus, and no lens respectively

D. No lens, plus, and minus respectively

Q5. What type of lens will you need to add if the far point of the patient’s eye is behind, in front of, and at the retinoscope?

A. No lens, minus, plus respectively

B. Minus, plus, and no lens respectively

C. Plus, no lens, minus respectively

D. Plus, minus, no lens respectively

Retinoscopy at the Working Distance (50 or 66cm)

• If you see a “with motion”, progressively add plus lenses until you reach neutralization

• If you see an “against motion”, progressively add minus lenses until you reach neutralization

• Once you have reached neutralization, note the lens that was needed….this is your gross refraction

• Subtract your working distance lens from the gross refraction to get the net or actual refraction:

• 66 cm = subtract 1.5 diopters

• 50 cm = subtract 2.0 diopters

Retinoscopy at 66 cm

•With no lens in place: • emmetropia, hyperopia, & myopia <1.5 D show “with” motion**•myopia 1.5 D shows neutralization•myopia >1.5 D shows “against” motion

• **This constitutes the large majority of our patients, so you are generally going to see a with motion when you begin your refraction

•What type of lens does a “with motion” want?

Examples at 66cm Working Distance

•Neutralization seen at +2.0D:

+2.0D (gross refraction)

(-) 1.5D (working distance)

+0.5D (net refraction)

Examples at 66cm Working Distance

•Neutralization seen at +0.5D:

+0.5D (gross refraction)

(-)1.5D (working distance)

-1.0D (net refraction)

Examples at 66cm Working Distance

•Neutralization seen at -1.5D:

-1.5D (gross refraction)

(-)1.5D (working distance)

-3.0D (net refraction)

Examples at 50cm Working Distance

•Neutralization seen at +3.0D:

+3.0D (gross refraction)

(-)2.0D (working distance)

+1.0D (net refraction)

Examples at 50cm Working Distance

•Neutralization seen at -1.0D:

-1.0D (gross refraction)

(-)2.0D (working distance)

-3.0D (net refraction)

Technique of Retinoscopy

• Dim room lights, assistant holds animal, directs gaze

• Retinoscope held in palm, keep finger or thumb on sleeve, lens bar in other hand

• Move sleeve down to set correct vergence,

• Rotate sleeve so a vertical streak projected on eye

• Set distance at 66 or 50 cm

• Try and keep both eyes open to prevent yourself from accommodating

Technique of Retinoscopy: Optical Alignment

• Purkinje images = reflections from the optical interfaces of the cornea and lens

• by moving your head position, align (superimpose) Purkinje images on anterior cornea and anterior lens capsule

• i.e. position yourself in relation to the eye such that only one Purkinje image is seen in the middle of the pupil

• note that, with our patients who are in constant motion, you need to constantly realign

Technique of Retinoscopy

• Move streak perpendicular to its axis….streak brought into pupil with slow, deliberate movement (slightly shake head back and forth or nod head up and down)

• Observe reflexes, add plus or minus lenses 1-2 cm (vertex distance) in front of the patient’s eye until you find neutralization

• Direction of beam is then rotated to produce horizontal streak and this meridian is assessed…ALWAYS ASSESS BOTH MERIDIANS

Identifying Neutrality

Characteristics of Retinoscopic Reflexes

Closer to Neutralization

Farther from Neutralization

Width Wide Narrow

Brilliance Bright Dull

Speed Fast Slow

Neutralization – complete illumination of entire pupillary area

Slide courtesy Dr. Paul Miller

Neutralization

Video courtesy of Dr. Paul Miller

Against motion (2D), neutralization (1.5D) with motion (1.0D) Neutralization

Duller – Narrower – Slower Brighter – Wider – Faster

Reflexes – Identifying Neutrality

Video courtesy Dr. Paul Miller

Reflexes – Against Motion, Neutralization, With Motion(model eye is being moved closer to examiner)

Video courtesy Dr. Paul Miller

Tips for Identifying Neutrality

• A “with” motion is much easier to see than an against motion

• Therefore, neutrality should be approached from the “with” side

• If you see a “with” motion with no lens in place, proceed with adding plus lens until you reach neutrality

• If you are not sure of what motion you are seeing with no lens in place, it is probably an against motion….you can confirm an against motion by raising the sleeve on your retinoscope, and an against motion “magically” becomes a “with” motion.

• Put the sleeve back down and add minus lens until you see a recognizable “with” motion, then bracket back to neutrality, i.e. always approach neutrality from the “with” side

Tips for Identifying Neutrality

• With lens bar in 0.5D and 1.0D increments, you may see a “with” motion with one lens and “against” with the next higher lens….in this case extrapolate between the two to define neutralization.

Confirming Neutrality

• neutrality not a point, but rather a zone between the last recognizable “with” motion and the first recognizable “against” motion

• judge endpoint slightly on the “with” motion side of this zone (point when last recognizable, slight “with” motion is seen)

• at neutralization, lean forward from 66 cm to observe with motion, lean backward from 66 cm to observe “against” motion…..(neutrality is also called the “reversal point”)

Quiz 2

Q1. If you see an against motion at your working distance with no lens in place, you can confirm it is an against motion by:

A. Raising the retinoscope sleeve and the against motion becomes more pronounced

B. Raising the retinoscope sleeve and the against motion becomes a with motion

C. Leaning in slightly closer to the patient and the against motion becomes a with motion

D. Leaning slight back from the patient and the against motion becomes a with motion

Q2. What retinoscopic reflex is seen most commonly in dogs with no working or corrective lens in place?

• With motion

• Against motion

• Neutralization

• A narrow streak

Q3. What are the characteristics of the retinoscopic reflex at neutralization?

A. Slow, dull, narrow beam

B. Slow, bright, narrow beam

C. Fast, bright, wide beam

D. Fast, bright, narrow beam

Q4. You find neutralization at your working distance. If you lean in (move slightly closer to the patient), and lean back (move slight further from the patient), what retinoscopic reflex will you see?

A. Against and with respectively

B. Against and neutralization respectively

C. With and against respectively

D. With and neutralization respectively

Q5. You find neutralization at a 66cm working distance at +3.0 diopters in both meridians. The patient is:

• Myopic

• Hyperopic

• Emmetropic

• Astigmatic

Q6. You find neutralization at a 50cm working distance at +0.5 diopters in both meridians. The patient is:

• Myopic

• Hyperopic

• Emmetropic

• Astigmatic

Astigmatism

• Astigmatism - an aspherical refractive error, caused when the refractivesurfaces of the eye have different curvature in different meridians,generally caused by difference in corneal curvatures. Such an eye two ormore points of focus on incident light rays.

Futball Football

Astigmatic Refractive Errors(DON’T WORRY ABOUT THESE, they are generally only

relevant in humans where the refractive error is corrected)

• Simple astigmatism• emmetropia/ametropic

• Compound astigmatism• hyperopia/hyperopia or myopia/myopia

• Mixed astigmatism• hyperopia/myopia

• Regular astigmatism

• Two principle meridians are 90 degrees apart (perpendicular)

• Irregular astigmatism

• Two principle meridians are not perpendicular

• Oblique astigmatism

• Regular astigmatism that is tilted so not at 90/180 degree configuration

Astigmatic Refractive Errors

• neutralization seen with different lenses in two different meridians

• or…when neutralization reached in one meridian, streak is rotated, either a “with” or an “against” motion is seen with same lens

• major or principle meridians:• least and most refractive meridians• generally oriented with axes at or

near 90 degrees and 180 degrees

45

90135

0180

45

90135

0180

Astigmatic Refractive Errors

• “Break” phenomena:• seen with oblique astigmatism

(where principle axes are not at 90 and 180 degrees) > 1.0D

• rotate beam with sleeve to line up the face band and pupil band of light and streak perpendicular to axis of beam, then rotate 90 degrees to refract the opposite meridian

Designating Refractive Error

• determine net refraction in both vertical and horizontal meridians

• if refraction is same in both meridians, eye is “spherical”, denoted as e.g. “0” D, -2.5 D or +2.5D

• if two meridians are different, eye is “astigmatic”:• designate two meridians with a “lens

cross”

+1.5D (horizontal beam

sweeping top to bottom)

+0.5D

(Vertical beam

sweeping side

to side)

The streak tests power in the direction of the sweep

vertical streak tests the horizontal or 180-degree meridian

horizontal streaks tests the vertical or 90-degree meridian

Estimating Hyperopia

• “enhancement” estimates gross hyperopia

• at working distance, compare thickness of beam in pupil (retinal band) vs. outside the pupil (face band)

• slowly change vergence by raising sleeve until the beam of light in the pupil the thinnest possible

Estimating Gross Hyperopia• Slowly raise sleeve until streak in pupil is as thin as possible (generally ~1/2 way up

the sleeve)

• High degrees (4-5D) of gross hyperopia = beam will become very thin

• Emmetropia = beam will thin slightly to ~3/4 width of face beam

• Myopia = beam will not enhance or thin

• Useful screening technique to begin retinoscopy

Emmetropia

+5.5 Diopters Hyperopia

Video courtesy Dr. Paul Miller

Estimating Myopia – Far Point Determination• if against motion observed at 66 cm, >1.5 D myopia present

• confirm against motion by moving sleeve up to observe a with motion

• move sleeve back down, using no lenses, slowly move progressively slower to eye, streaking beam until neutralization reached

• estimate your distance from the eye at neutrality:

• i.e. 3 D of myopia will have a far point at 33 cm

• 5 D of myopia will have a far point at 20 cm

Estimating Myopia

Raise sleeve to confirm against motionWith no lenses in place, move towards eye, find neutrality, move closer to see a with motion, then back up to neutrality, estimate distance from eye

Video courtesy Dr. Paul Miller

Should you dilate the pupil to perform retinoscopy?

• In our patients, generally best performed without mydriasis

• Cycloplegia/mydriasis used in humans to eliminate accommodation

• While retinoscopy results not significantly different with and without mydriasis in dogs and horses, mydriasis reduces accuracy in identifying neutrality due to spherical aberration:

• full mydriasis often causes swirling or “scissors” motion• if mydriasis present, concentrate on center of pupil

Geocities.wsCorboy

Practical Aspects of Veterinary Retinoscopy

• good assistant to restrain patient is invaluable

• estimating technique for gross hyperopia useful to perform first and reduce refraction time…..indicates if the patient is near emmetropic, is hyperopic, or is myopic.

• tapetum makes retinoscopy more challenging in dogs v. humans, but the brightness of the reflection from the tapetum is useful in identifying neutrality

Accuracy of Retinoscopy

•most inaccurate measurements are the result of 1)incorrect sleeve position, 2)an incorrect working distance or 3)poor optical alignment

• check sleeve position, measure working distance when learning technique, and constantly optically realign by centering Purkinje images

Quiz 3

Q1. At 66 cm, you find neutralization at +3.5 in the vertical meridian and +2.5 in the horizontal meridian. The patient is:

A. 1 diopter astigmatic and hyperopic

B. 1 diopter astigmatic and myopic

C. 1 diopter astigmatic and emmetropic

D. 1.5 diopter astigmatic and hyperopic

Q3. At the working distance, you gradually raise the retinoscope sleeve until the beam in the pupil is as thin or narrow as you can make it. What is the nature of this beam (streak) in a hyperope, emmetrope, and myope?

A. Slightly narrow, very narrow, and broad respectively

B. Broad, slightly narrow, very narrow respectively

C. Very narrow, slightly narrow, and broad respectively

D. Very narrow, broad, and slightly narrow respectively

Q4. At 66 cm, you see an against motion, you confirm this against motion and then move in towards the patient and find neutralization at 50cm. The refractive error in this patient is:

A. -2.0 diopters

B. -1.5 diopters

C. +2.0 diopters

D. +1.5 diopters

SLACK INTERNATIONAL BOOK DISTRIBUTORS

AN EXCELLENT, EASY TO UNDERSTAND INTRODUCTION TO RETINOSCOPY

Retinoscopy Training Eyes

Retinoscopy Simulator

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