Anatomy Of Eye Mohammad Ali A Sadiq, M.D F.C.P.S (Pk) F.P.O.S (UK) F.A.A.P.O.S (Harvard) Assistant Professor of Ophthalmology King Edward Medical University

EYE Asymmetrical globe about an inch in diameter (24mm) Cornea (Clear dome over the iris) Conjuctiva (thin layer of tissue covering the front of eye) Sclera (White part) Iris (pigmented part) Pupil

EYE Lens – behind the iris and pupil Focus light on the back of the eye Vitrous – Gel filling the eye Retina – special light sensing cells Converts light into electrical impulses Macula – small sensitive Area in the center of retina Optic Nerve –carries Impulses to the brain

Eyelid Thin fold of skin that covers and protects the human eye. FUNCTIONS Regularly spread the tears and other secretions of the eye surface. Responsible for corneal protection Responsbile for corneal nutrition Lashes provide additional protection

Eyelid LAYERS Skin Sweat glands Sebacoues glands Hair – eye lashes Subcuatneous tissue Orbicularis Oculi muscle Orbital septum Aponeurotic fat Levator palpebrae superioris Muller muscle Tarsal Plate Palperbral Conjuctiva

Lacrimal system LACRIMAL GLAND PUNCTI LACRIMAL CANALICULI LACRIMAL SAC Secretes tears PUNCTI 0.3mm in diamter Sits on an elevated mound – papilla lacrimalis Relatively avascular LACRIMAL CANALICULI Initial vertical segment – 2mm Horizontal segment -- 8mm Valve of Resonemuller LACRIMAL SAC Fundus – 3-5 mm Body – 10 mm NASOLACRIMAL DUCT 12mm Intraosseous portion 5 mm inferior membranous portion Valve of Hassner

CORNEA Transparent from part of the eye covering the Iris, pupil and Anterior chamber Accounts for Approx 2/3rd of the refractive power of the eye (43 Diopters) Completely avascular – recieves nutrients via diffusion from the tear film and aqueous humor Unmyelinated nerve endings sensitive to

CORNEA Diameter – 11.5 mm Thickness Layers 0.5-0.6 mm in the center 0.6-0.8 mm in the periphery Layers Corneal Epithelium – non keratinized stratified sq cells Bowmans Layer – Anterior limiting membrane (Type 1 collagen fibrils) Corneal Stroma – regularly arranged collagen fibrils with keraotcytes (Type 1 collagen fibrils) Descement’s membrane – Posterior limiting membrane (Type 1 and 4 collagen fibrils) Corneal Endothelium simple squamous or low cuboidal monolayer

AQUEOUS HUMOR Transparent, gelatinous fluid similar to plasma but low in protein. FUNCTIONS: Maintains the IOP Provided nutrition to Cornea Trabecular meshwork Lens Anterior Vitrous Presence of Immunoglobulins Refractive Index

AQUEOUS HUMOR Secreted into the posterior chamber by the ciliary body – pars plicata Drains out of the eye through the trabecular meshwork Then into the schlem canal Directly into episcleral vein Indirectly through collector channels

Conjuctiva Lines the inside of the eyelids and covers the sclera Non keratinized stratified epithelium with goblet cells FUNCTION Helps lubricate the eye by producing mucus and lacrimal gland Contributes to immune surveillance of the eye

Conjuctiva Palpebral or Tarsal conjuctiva Bulbar or Ocular Conjuctiva Lines the eyelid Bulbar or Ocular Conjuctiva Covers the eyeball over the sclera Tightly bound to underlying sclera by Tenon’s capsule Moves with eyeball movement Fornix Conjuctiva Junction between bulbar and Palpebral conjuctiva Loose and flexible

Sclera Forms the supporting wall of the eyeball Continuous with the clear cornea Thickest in the area surrounding the optic nerve Thinnest at the insertion of the muscle

SCLERA Three Divisions Episclera Sclera Proper Lamina Fusca Loose connective tissue immediately beneath the conjuctiva Sclera Proper Dense white tissue that gives the area its colour Lamina Fusca Inner most zone made up of elastic fibres

IRIS Thin, circular structure in the eye responsible for controlling the diameter and size of the pupil TWO LAYERS Storma Front pigmented fibrovascular layer Connects to Spincter muscle – sphincter pupillae Dilator muscle – Dilator pupillae Pigmented Epithelial cells Two cell thick

IRIS Outer edge of the iris is attached to Sclera Anterior ciliary body IRIS AND CILIARY BODY TOGETHER ARE KNOWN AS ANTERIOR UVEA PORTIONS OF THE IRIS Pupillary zone – inner region whose edge forms the boundary of the pupil Cilliary Zone – rest if the iris that extends to its origin at the ciliary body Collarette – region when the sphincter and dilator muscle overlap

LENS Transparent bi-convex structure Helps in refracting light (18 diopters) – one third of the eyes total power Ability to change shape – Accomodation Suspended in place by the suspensory ligaments 10 mm in diameter. Axial length of 4mm

LENS COMPONENTS OF LENS LENS CAPSULE LENS EPITHELIUM LENS FIBERS Smooth transparent basement membrane Elastic membrane composed of collagen (type 4) Varies from 2 to 28 micrometers – thickest at the equator LENS EPITHELIUM Anterior portion of the lens between the capsule and lens fibers Simple cuboidal epithelium Regulates most of the homostatic functions of the lens Progenitor for new lens fibers LENS FIBERS Bulk of the lens Long, thin , transparent cells, firmly packed. Diameters typically 4-7 microns and length upto 12 mm

VITROUS Clear gel filling the space between retina and the lens Remains unchanged throughout life Produced by cells in the non pigmented portion of the ciliary body 98-99% of the body is water Strongly connected to the optic disc and the orra serrata Loosely connected to the macula and blood vessels As human ages, it liquefies and often collapses

CHOROID Thin vascular layer between the sclera and the retina Supplies blood to the retina and conducts arteries and nerves to other structures in the eye FOUR LAYERS Haller’s layer – outermost layer consisting of large blood vessels Sattler’s layer – layer of medium diameter blood vessles Choriocapillaris – layer of capillaries Bruch’s membrane – Inner most layer of the choroid

RETINA L atin word “rete” meaning net Inner most, light sensitive layer of the eye Light striking the retina initiates a cascade of chemical and electrical events that trigger a nerve impulse PHOTORECEPTOR CELLS RODS Dim light Black and white vision CONES Suuport day time vision Colour perception Ganglion cells Reflexive response to bright daylight

RETINA LAYERS OF RETINA Inner Limiting membrane Nerve Fiber layer – axons of ganglion cell nuclei Ganglion cell layer Inner Plexiform layer – Contains synapses between bipolar axons and denrites of ganglion and amacrine cells Inner Nuclear Layer – contains the nuclei of amacrine cells Outer pelxiform layer – projections of rods and cones Outer nuclear layer – cell bodies of rods and cones External limiting membrane layer – layer that separates the inner segment portions of the photoreceptors from their cell nucleus Layer of rods and cones Retinal Pigment Epithelium - single layer of cuboidal cells. This is closest to the choroid.

EXTRA-OCULAR MUSCLES 6 Extra-ocular muscles 4 Rectus muscles 2 Oblique muscles M.R – 5.5mm from limbus I.R ``– 6.5 mm L.R -- 6.9 mm S.R -- 7.7mm

OPTIC NERVE Extension of the brain Energy transmission from retina to the brain Subject to underdevelopment, damage. Inflammation Over 1 million nerve fibers Once it is severed, it cannot be reconnected

THANK YOU