Ophthalmology 5th year, 1st 2 lectures (Dr. Bakhtyar)

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Introduction to Introduction to ophthalmology ophthalmology By By Dr.Bakhtiar Q. Jaf Dr.Bakhtiar Q. Jaf

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The lecture has been given on Oct. 4th, 2010 by Dr. Bakhtyar.

Transcript of Ophthalmology 5th year, 1st 2 lectures (Dr. Bakhtyar)

Page 1: Ophthalmology 5th year, 1st 2 lectures (Dr. Bakhtyar)

Introduction to Introduction to ophthalmologyophthalmology

ByBy

Dr.Bakhtiar Q. JafDr.Bakhtiar Q. Jaf

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Objective of the lectureObjective of the lecture

►To give a simple introduction to To give a simple introduction to clinical anatomy, physiology & clinical anatomy, physiology & embryology of the eyeembryology of the eye TO recognize clinical approach to the TO recognize clinical approach to the

eye complaints eye complaints

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AnatomyAnatomy ofof thethe eyeeyeThe The eyeballeyeball, or , or globeglobe, sits in a protective , sits in a protective bony structure known as the orbit. Lined bony structure known as the orbit. Lined with muscle, connective and adipose with muscle, connective and adipose tissues.tissues.the the orbitorbit is about 4 cm in height, width, is about 4 cm in height, width, and depth and is shaped roughly like a and depth and is shaped roughly like a four-sidedfour-sided pyramid pyramidsurrounded on three sides by the surrounded on three sides by the sinusessinuses: : The The ethmoidethmoid (medially), the (medially), the frontalfrontal (superiorly), and the (superiorly), and the maxillarymaxillary (inferiorly). (inferiorly). The optic nerve and the ophthalmic The optic nerve and the ophthalmic arteryartery enter the orbit at its apex through enter the orbit at its apex through the optic foramenthe optic foramen..

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EyelidsEyelids protect the anterior portion of protect the anterior portion of the eye , composed of thin elastic the eye , composed of thin elastic skin that covers striated and smooth skin that covers striated and smooth muscles & the tarsal plates. muscles & the tarsal plates. TearsTears are vitally important to the are vitally important to the health of the anterior segment of the health of the anterior segment of the eye. They are formed by the main eye. They are formed by the main lacrimal gland and the accessory lacrimal gland and the accessory lacrimal glands.lacrimal glands. The The conjunctivaconjunctiva, a mucous , a mucous membrane, provides a barrier to the membrane, provides a barrier to the external environment and nourishes external environment and nourishes the eyethe eye..

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The The sclerasclera,, commonly known as the "white commonly known as the "white of the eye," is a of the eye," is a densedense fibrousfibrous structure structure that composes the posterior five sixths of that composes the posterior five sixths of the eyethe eyeThe The corneacornea a transparent avascular a transparent avascular domelike structure, forms the most domelike structure, forms the most anterior portion of the eyeball and is the anterior portion of the eyeball and is the main refracting surface of the eye. Behind main refracting surface of the eye. Behind the cornea lies the the cornea lies the anterioranterior chamberchamber, , filled filled with a continually replenished supply of with a continually replenished supply of clear aqueous humor, which nourishes the clear aqueous humor, which nourishes the corneacornea..

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TheThe uvea uvea consists of the iris, the consists of the iris, the ciliary body, and the choroid. The ciliary body, and the choroid. The iris, or colored part of the eye, is a iris, or colored part of the eye, is a highly vascularized, pigmented highly vascularized, pigmented collection of fibers surrounding the collection of fibers surrounding the pupil. The pupil. The pupilpupil is a space that is a space that dilates and constricts in response dilates and constricts in response to lightto light..

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Directly behind the pupil and iris Directly behind the pupil and iris lies the lies the crystallinecrystalline lenslens, a colorless , a colorless and almost completely transparent and almost completely transparent biconvex structure held in position biconvex structure held in position by zonular fibers. It is avascular by zonular fibers. It is avascular and has no nerve or pain fibers.and has no nerve or pain fibers. The lens is suspended behind the The lens is suspended behind the iris by the iris by the zonuleszonules and is and is connected to the ciliary body. The connected to the ciliary body. The ciliary bodyciliary body controls controls accommodation through the accommodation through the zonular fibers and the ciliaryzonular fibers and the ciliary musclesmuscles..

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The posterior chamber is a small space between the vitreous and the iris. Aqueous fluid is manufactured in the posterior chamber by the ciliary body The choroid is layered between the retina and

the sclera and is a highly vascularised tissue, supplying blood to the adjacent outer portion of the retina.The ocular fundus is the largest chamber of the

eye and contains the vitreous humor, a clear gelatinous substance, mostly water, encapsulated by a hyaloid membrane, the vitreous humor.

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visualvisual pathwaypathway Good Good visionvision is not dependent solely is not dependent solely

on a healthy functioning eyeball on a healthy functioning eyeball but also on an intact but also on an intact visualvisual pathwaypathway. This pathway is made . This pathway is made up of the retina, optic nerve, optic up of the retina, optic nerve, optic chiasma, optic tracts,chiasma, optic tracts,lateral geniculate bodies, optic lateral geniculate bodies, optic radiations & radiations & the visual cortex of the occipital the visual cortex of the occipital lobe.lobe. The pathway is an extension of The pathway is an extension of the central nervous system. The the central nervous system. The optic nerve is the second cranial optic nerve is the second cranial nerve. Its function is to transmit nerve. Its function is to transmit visual impulses from the retina to visual impulses from the retina to the higher centers in the brain. the higher centers in the brain.

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EmbryologyEmbryology ofof thethe eyeeyeThe eye is formed from both The eye is formed from both ectodermectoderm and and mesenchymemesenchyme. The . The neuroectodermneuroectoderm that is that is derived from the neural tube gives rise to derived from the neural tube gives rise to (the retina, the fibers of the optic nerve, (the retina, the fibers of the optic nerve, and the smooth muscle of the iris). The and the smooth muscle of the iris). The surface ectodermsurface ectoderm on the side of the head on the side of the head forms( the corneal and conjunctival forms( the corneal and conjunctival epithelium, the lens, and the lacrimal and epithelium, the lens, and the lacrimal and tarsal glands). Thetarsal glands). The mesenchymemesenchyme forms( the forms( the corneal stroma, the sclera, the choroid, the corneal stroma, the sclera, the choroid, the iris, the ciliary musculature, part of the iris, the ciliary musculature, part of the vitreous body, and the cells lining the vitreous body, and the cells lining the anterior chamber)anterior chamber)..

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The rudimentary eyeball develops as an The rudimentary eyeball develops as an ectodermal ectodermal diverticulumdiverticulum from the lateral from the lateral aspect of the forebrain. The diverticulum aspect of the forebrain. The diverticulum grows out laterally toward the side of the grows out laterally toward the side of the head, and the end becomes slightly dilated head, and the end becomes slightly dilated to form the to form the optic vesicleoptic vesicle, , while the while the proximal portion becomes constricted to proximal portion becomes constricted to form the form the optic stalkoptic stalk. . At the same time, a small area of surface At the same time, a small area of surface ectoderm overlying the optic vesicle ectoderm overlying the optic vesicle thickens to form thethickens to form the lens placodelens placode. . The The lens placode invaginates and sinks below lens placode invaginates and sinks below the surface ectoderm to become the the surface ectoderm to become the lens lens vesiclevesicle, the optic vesicle becomes , the optic vesicle becomes invaginated to form the double-layered invaginated to form the double-layered optic cupoptic cup..

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► At end of 4At end of 4thth week of pregnancy; Optic week of pregnancy; Optic Vesicle contact with surface ectoderm & Vesicle contact with surface ectoderm & invaginate to form Optic cup & the lens invaginate to form Optic cup & the lens vesiclevesicle

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TheThe opticoptic nervenerveThe ganglion cells of the retina The ganglion cells of the retina develop develop axonsaxons that converge to a that converge to a point where the optic stalk leaves point where the optic stalk leaves the posterior surface of the optic the posterior surface of the optic cup. This site will later become the cup. This site will later become the optic discoptic disc. . The axons now pass among the The axons now pass among the cells that form the inner layer of cells that form the inner layer of the stalk. Gradually, the inner the stalk. Gradually, the inner layer encroaches on the cavity of layer encroaches on the cavity of the stalk until the inner and outer the stalk until the inner and outer layers fuselayers fuse..

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The Ocular ExaminationThe Ocular Examination Visual AcuityVisual AcuityAfter the patient's chief complaint and history After the patient's chief complaint and history have been established, visual acuity should be have been established, visual acuity should be assessed. This is an essential part of the eye assessed. This is an essential part of the eye examination and a measure against which all examination and a measure against which all therapeutic outcomes are based.therapeutic outcomes are based. Most health care providers are familiar with the Most health care providers are familiar with the standard Snellen chart. This chart is composed standard Snellen chart. This chart is composed of a series of progressively smaller rows of of a series of progressively smaller rows of letters and is used to test distance vision.letters and is used to test distance vision. The fraction 6/6 is considered the standard of The fraction 6/6 is considered the standard of normal vision. Most people can see the letters normal vision. Most people can see the letters on the line designated as 6/6 from a distance of on the line designated as 6/6 from a distance of 6 meters6 meters . .

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The External Eye ExaminationThe External Eye ExaminationAfter the visual acuity has been After the visual acuity has been recorded, an external eye recorded, an external eye examination is performedexamination is performedDIAGNOSTIC EVALUATIONDIAGNOSTIC EVALUATION DIRECT OPHTHALMOSCOPYDIRECT OPHTHALMOSCOPY Is a hand-held instrument with Is a hand-held instrument with varying plus and minus lenses. varying plus and minus lenses. The lenses can be rotated into The lenses can be rotated into place, enabling the examiner to place, enabling the examiner to bring the cornea, lens, and retina bring the cornea, lens, and retina into focusinto focus

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Indirect OphthalmoscopyIndirect Ophthalmoscopy Is an instrument commonly used by the Is an instrument commonly used by the ophthalmologist. It produces a bright and ophthalmologist. It produces a bright and intense light. The light source is fixed with intense light. The light source is fixed with a pair of binocular lenses, which are a pair of binocular lenses, which are mounted on the examiner's head. The mounted on the examiner's head. The ophthalmoscope is used in conjunction ophthalmoscope is used in conjunction with a hand-held 20-dioptcr lens. This with a hand-held 20-dioptcr lens. This instrument enables the examiner to see instrument enables the examiner to see larger areas of the retina, although in an larger areas of the retina, although in an unmagnified stateunmagnified state..

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Slit-Lamp ExaminationSlit-Lamp ExaminationIs a binocular microscope mounted on a table. This instrument Is a binocular microscope mounted on a table. This instrument enabls the user to examine the eye with magnification of 10 to 40 enabls the user to examine the eye with magnification of 10 to 40 times the real image. times the real image. Color Vision TestingColor Vision TestingBecause alteration in color vision is sometimes Because alteration in color vision is sometimes indicative of optic nerve problems, color vision indicative of optic nerve problems, color vision testing is often performed in a neuro-testing is often performed in a neuro-ophthalmologic workup. ophthalmologic workup. UltrasonographyUltrasonographyLesions in the globe or the orbit may not be Lesions in the globe or the orbit may not be directly visible and are evaluated by ultrasound.directly visible and are evaluated by ultrasound.Color Fundus PhotographyColor Fundus PhotographyFundus photography is a technique used to detect Fundus photography is a technique used to detect and document retinal lesions. The patient's pupils and document retinal lesions. The patient's pupils are widely dilated during the procedure, and visual are widely dilated during the procedure, and visual acuity is diminished for about 30 minutes due to acuity is diminished for about 30 minutes due to retinal "bleaching" by the intense flashing lightsretinal "bleaching" by the intense flashing lights..

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TonometryTonometry is used to measure IOP by determining the amount of force necessary to indent or flatten (applanate) a small anterior area of the globe of the eye.GonioscopyGonioscopy is used to visualize the angle of the anterior chamber to identify abnormalities in appearance and measurements.Perimetry TestingPerimetry testing is used to evaluate the field of vision. A visual field is the area or extent of physical space visible to an eye in a given position. Its average extent is 65 degrees upward, 75 degrees downward, 60 degrees inward, and 95 degrees outward when the eye is in the primary gaze.

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IMPAIRED VISION REFRACTIVE ERRORS In refractive errors, vision is impaired because

a shortened or elongated eyeball prevents light rays from focusing sharply on the retina. Blurred vision due to refractive error can be corrected with eyeglasses and contact lenses.

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Those patients for whom the visual image focuses precisely on the macula and who do not need eye glasses or contact lenses are said to have emmetropia.

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People with myopia have deeper eyeballs; the distant visual image focuses in front of, or short of, the retina. These people are nearsighted and are termed myopic and experience blurred distance vision.

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When people have a shorter depth to their eyes, the visual image focuses beyond the retina; the eyes are more shallow and are termed hyperopic. People who have hyperopia are farsighted.

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GLAUCOMAGLAUCOMAGlaucoma is the term used to describe a Glaucoma is the term used to describe a group of ocular conditions characterized by group of ocular conditions characterized by optic nerve damage, high intraocular optic nerve damage, high intraocular pressure and visual field deffect.pressure and visual field deffect. CLASSIFICATION OF GLAUCOMACLASSIFICATION OF GLAUCOMAGlaucoma canGlaucoma can be be open angle open angle or or angle angle closure, closure, depending on which mechanisms depending on which mechanisms cause the impairment of the aqueous cause the impairment of the aqueous outflow. Glaucoma can also be primary or outflow. Glaucoma can also be primary or secondary, depending on whether secondary, depending on whether associated factors contribute to the rise in associated factors contribute to the rise in IOPIOP..

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CATARCTCATARCTA cataract is a lens opacity or A cataract is a lens opacity or cloudinesscloudinessClinical ManifestationsClinical ManifestationsPainless blurring of vision is Painless blurring of vision is characteristic of cataractscharacteristic of cataracts..

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Commonly Used Ocular MedicationsCommonly Used Ocular MedicationsTopical AnestheticsTopical AnestheticsOne to two drops of proparacaine One to two drops of proparacaine hydrochloride and tetracaine hydrochloride and tetracaine hydrochlorid are instilled before hydrochlorid are instilled before diagnostic procedures such as tonometry diagnostic procedures such as tonometry and gonioscopy and in minor ocular and gonioscopy and in minor ocular procedures such as removal of sutures or procedures such as removal of sutures or conjunctival or corneal scrapings.conjunctival or corneal scrapings.Mydriatics and CycloplegicsMydriatics and CycloplegicsMydriasis, or pupil dilation, is the main Mydriasis, or pupil dilation, is the main objective of the administration of objective of the administration of mydriatics and cycloplegicsmydriatics and cycloplegics

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Anti-lnfectivesAnti-lnfectivesAnti-infective medications include Anti-infective medications include antibiotics, antifungals, and antibiotics, antifungals, and antivirals. Most are available as antivirals. Most are available as drops, ointments, or subconjunctival drops, ointments, or subconjunctival or intravitreal injections. Antibiotics or intravitreal injections. Antibiotics include penicillin, the cephalosporins, include penicillin, the cephalosporins, aminoglycosides, and aminoglycosides, and fluoroquinolones. The main antifungal fluoroquinolones. The main antifungal agent is amphotericin B. Antivirals agent is amphotericin B. Antivirals include acyclovir and ganciclovirinclude acyclovir and ganciclovir . .

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Corticosteroids and Nonsteroidal Anti-Inflammatory DrugsThe topical preparations of corticosteroids are commonly used in inflammatory conditions of the eyelids, conjunctiva, cornea, anterior chamber, lens, and uvea. In posterior segment diseases that involve the posterior sclera, retina, and optic nerve, the topical agents are less effective; hence, the parenteral and oral routes are preferred.

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ReferencesReferences1. Lecture notes 1. Lecture notes

in ophthalmology in ophthalmology 2. Parson’s 2. Parson’s

disease of the eyedisease of the eye

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