OPTOM FASLU MUHAMMED

Eye lid In addition to tear spreading, the eyelid is

primarily responsible for corneal nutrition Also provides protection to corneaLashes offer additional protection

Lacrimal System/Tear FilmLacrimal system is responsible for tear

production and drainageMade up of 3 layers Created primarily by lacrimal apparatus

and meibomian glandsLubricate the eyeball, provides

oxygen/nutrition for cornea, has antibacterial properties and helps wash away debris

Also have unique composition which keeps surface of cornea slick.

Lacrimal System

CorneaMade up of 5 layersSpecialized Transparent Tissue

No blood vesselsPrimarily responsible for refracting light

Does more of the job than the lensMore nerve endings than anywhere else in

the bodyProtection to the eye

The only part of the eye that is transplanted from one person to another

Aqueous humorFills space between cornea and iris Continuously produced by ciliary bodyFlows into ant chamber through the pupilDrains from eye through trabecular meshwork to

canal of schlemmNourishes the cornea and lensGives front of eyeball form and shape

Anterior chamber is area between the cornea and the iris: filled with aqueous

Posterior chamber is the area behind the iris and in front of the lens: filled with aqueous

LimbusJunction between the cornea and the sclera Nourishes peripheral cornea…assists in

corneal wound healingPathway for aqueous outflow (contains

trabecular meshwork and canal of schlemm)

ConjunctivaThin translucent mucous membrane starts

at the limbus and covers the sclera and inner surface of the eyelid

Has some responsibility of tear production Subject to infection…problems from

contact lens use Can be degraded by environmental

conditions heat, wind, dust, etc.

ScleraWhite of the eyeMade up of 3 layersTough, fibrous tissue: site of extra-ocular

muscle attachmentOpaque...allows no light to enter Subject to inflammation

Iris The colored part of the eye…unique to every

individual like a fingerprintColor is dependent on the amount of pigment

A diaphragm, the iris has tiny muscles that control the light levels in the eye

Has 2 layersPupil is located in the center of the iris

pupil = hole: it is not an eye structure

LensTransparent, biconvex structure, held in place by

ciliary zonules Composed of 6 layersRefracts light Nutrition comes from aqueous humor…insoluble

deposits of proteins build up over time = cataractsA clouding of the lens and capsule

Live long enough and you WILL have some degree of cataract

cataracts also caused by other agents

Ciliary body Connects the choroid with the irisHas three parts including:

The ciliary muscle is ring shaped muscle that controls the shape of the lens (accommodation)

The ciliary process is the attachment site for the zonules and produces the aqueous in the pars plicata

The ciliary ring is attached to the choroid and is composed of the pars plana. The pars plana has no known function in the post-fetal eye thus this is a safe area through which surgical instruments may be inserted

Zonules Attach the lens to the ciliary bodyMay become broken or stretched causing the

lens to move out-of-place

Vitreous A thick, transparent gel like substance that fills

the center of the eyeball, giving it form and shapeA canal runs through the vitreous from optic disc

to the lens. It is a developmental leftover from the hyaloid artery. Usually regresses but may persist and result in floaters

May see reference to hyaloid membrane. This transparent tissue surrounds the vitreous and separates it from the retina

Central retinal veins and arteries extend in bundles, exit and enter respectively through the optic nerve

ChoroidA brown vascular sheet lying between the

sclera and the retinaOne of the route of blood supply for the

retina

Retina Most internal layer of eye, facing the vitreousConverts light energy into electrical energy

which is then sent to the brain via the optic nerveComposed of 10 layers…contains photoreceptors:

cones, near center (responsible for seeing detail and color) and rods, in periphery (responsible for seeing in low light and seeing movement)

Point of sharpest vision is in the fovea; located in the center of the macula

Ora SerrataA serrated juncture between the retina and

ciliary body marking the transition between non-sensitive tissue and the retinal portion with many layers and specialized photoreceptor cells

Intra-ocular musclesPurpose is to move eyes Maintain binocularity6 muscles

medial rectus (MR)—moves the eye toward the nose lateral rectus (LR)—moves the eye away from the nosesuperior rectus (SR)—primarily moves the eye upward

and secondarily rotates the top of the eye toward the nose inferior rectus (IR)—primarily moves the eye downward

and secondarily rotates the top of the eye away from the nose

superior oblique (SO)—primarily rotates the top of the eye toward the nose and secondarily moves the eye downward

inferior oblique (IO)—primarily rotates the top of the eye away from the nose and secondarily moves the eye upward

Optic NervePurpose is for energy transmission to brainSubject to underdevelopment, damage,

inflammation Contains over 1 million nerve fibers…once

severed cannot be reconnected=no “eye transplant”

Upon examination only the head can be seen by doctor. Should appear as yellowish pink, flat and with distinct margins

The cup to disc ratio is evaluation as a measure of health…increase in size of cup may indicate elevated pressure

Optic Nerve Pathways/Visual Cortex Message is carried down the optic nerve through

pathways to occipital cortex; here vision becomes sight

At the optic chiasma, the nasal nerve fibers cross; temporal nerve fibers go straight back to cortex; this arrangement impacts on visual fields

Results in visual field losses can be predicted based on where damage is located on the optic nerve