OPHTHALMOLOGY

OPHTHALMOLOGY

EYE AND ITS DISEASES

OBJECTIVES

References Functions of the eye; three steps of vision Why two eyes ? External features Eye ball (Cross section , coats, segments) Lacrimal apparatus and tear film Areas of special interest ( extraocular muscles , angle of ant. Chamber, retina, visual pathway) Bony orbit

RECOMMENDED TEXTBOOKS

PARSON KANSKI (CLINICAL OPHTHALMOLOGY) OPHTHALMOLOGY F0R UNDERGRADUATES BASIC AND CLINICAL SCIENCE COURSE (AAO) BASIC OPHTHALMOLOGY (AAO)


Function of the eye is sense of Vision Steps of vision are :1.Perception 2.Fusion 3.Stereopsis(percepti- on of depth) Two eyes for 1.increasing the field 2.Improving vision 3.perception of depth 4.overcoming the blind spot

EYE BALL

Sphere…24mmTwo poles…Ant. (center of the cornea) …post. (between the optic disc & the fovea).Three concentric coats :..Outer fibrous ..Middle vascular ..Inner nervous

1-OUTER FIBROUS LAYER

A- Cornea: ant. Transparent 1/6th. *Light Entry (transmission). *Light Refraction (40 diopters out of total 60 diopters) *Protective B- Sclera : post opaque white 5/6th . * Provides dark environment to improve contrast. * Insertion of extraocular muscles. * Protective. * Exit of optic nerve fibers through a posterior opening (lamina cribrosa). C- Limbus: corneoscleral junction


2- MIDDLE VASCULAR LAYER (UVEA)
Iris : vertical muscular diaphragm behind the cornea, perforated at its center (pupil). It has two muscles(….). *Regulates amount of light entering the eye depending on ambient light condition. *Prevents peripheral rays entering (stop effect)B. Ciliary body : posterior continuation of the iris. Triangular in section. * Gives attachment to the zonules which suspend the lens behind the pupil. * Contraction of ciliary muscles is responsible for the lens accommodation. * Secretion of aqueous humor from the ciliary epithelium.C. Choroid : the posterior most part of the uvea.It lines the sclera & nourishes the outer sublayers of retina and the macula including the fovea.

Uveal Tract Parts

3-INNER NERVOUS LAYER (RETINA)
Light sensitive layer changes light energy into an electrical impulse (Phototransduction). Very thin transparent layer that lines the choroid. Anteriorly it reaches the Ora Serrata. Posteriorly it ends around the optic disc. Two main sublayers..Outer Retinal Pigment epithelium(RPE) &..Inner Sensory Retina (Neuroretina) which is subdivided into nine layers Macula Fovea

EYE BALL SEGMENTS & CHAMBERS

The Crystalline Lens is suspended by zonules to the ciliary body.The lens & its zonules divide the eye ball into two segments:Anterior segment: *Boundaries… *Contains Aqueous HumorPosterior segment: *Boundaries… *contains Vitreous HumorThe anterior segment is further subdivided by the iris intoAnterior chamber Posterior Chamber

AQUEOUS HUMOR CIRCULATTION

Dynamic equilibriumSecretion :from the Non Pigmented ciliary Epithelium...post. chamber…pupil…ant. Chamber (AC)…Drainage: Angle of the ant. Chamber…Trabecular meshwork…Canal of Schlemm…Collector channels…Episcleral venous plexus…Ciliary veins …Systemic circulation.Functions of the Aqueous humor:1- Acts as blood or lymph to provide nutrients & take waste products from the avascular cornea and lens.2- Light transmission and refraction.3- Responsible for the IOP.

BONY ORBITS

Two quadrilateral pyramidal cavities in the skull. Each has …Apex (posterior) …Base (anterior) …Four walls Each contains ...Eye ball …Extraocular muscles …Vessels & nerves …Lacrimal gland …Lacrimal sac …Orbital fatEach communicates….with the cranial cavity thrugh: 1- Optic foramen 2- Superior orbital fissure ….with the pterygoid fossa through: Inferior orbital fissure

The bony orbit Walls

OCULAR ADNEXAE

Eye lids : two movable mucocutaneous folds, Conjunctiva : mucous membrane lining the eye lids and covering the anterior part of sclera. Lacrimal apparatus: A- Secretory system B- Drainage system.

EXTRAOCULAR MUSCLES

7 = 4+2+1 From the Orbit to the Sclera L6 . SO4 / 3

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