Ocular anatomy

Eye lid
In addition to tear spreading, the eyelid is primarily
responsible for corneal nutrition
Also provides protection to cornea
Lashes offer additional protection

Lacrimal System/Tear Film
Lacrimal system is responsible for tear production
and drainage
Made up of 3 layers
Created primarily by lacrimal apparatus and
meibomian glands
Lubricate 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.

Cornea
Specialized Transparent Tissue
No blood vessels
Primarily responsible for refracting light
Does more of the job than the lens
More nerve endings than anywhere else in the
body
Protection to the eye
The only part of the eye that is transplanted from
one person to another

Aqueous humor
Fills space between cornea and iris
Continuously produced by ciliary body
Flows into ant chamber through the pupil
Drains from eye through trabecular meshwork to canal of
schlemm
Nourishes the cornea and lens
Gives 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

Limbus
Junction between the cornea and the sclera
Nourishes peripheral cornea…assists in corneal
wound healing
Pathway for aqueous outflow (contains trabecular
meshwork and canal of schlemm)

Conjunctiva
Thin 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.

Sclera
White of the eye
Tough, fibrous tissue: site of extra-ocular muscle
attachment
Opaque...allows no light to enter
Subject to inflammation

Iris
The colored part of the eye…unique to every individual
like a fingerprint
Color is dependent on the amount of pigment
A diaphragm, the iris has tiny muscles that control the
light levels in the eye
Has 2 layers
Pupil is located in the center of the iris
pupil = hole: it is not an eye structure

Lens
Transparent, biconvex structure, held in place by ciliary
zonules
Composed of 6 layers
Refracts light
Nutrition comes from aqueous humor…insoluble deposits
of proteins build up over time = cataracts
A 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 iris
Has 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 body
May 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 shape
A 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

Choroid
A brown vascular sheet lying between the sclera and
the retina
One of the route of blood supply for the retina

Retina
Most internal layer of eye, facing the vitreous
Converts light energy into electrical energy which is then
sent to the brain via the optic nerve
Composed 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 Serrata
A 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 muscles
Purpose is to move eyes
Maintain binocularity
6 muscles
medial rectus (MR)—moves the eye toward the nose
lateral rectus (LR)—moves the eye away from the nose
superior 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 Nerve
Purpose is for energy transmission to brain
Subject 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

Ocular anatomy

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