The document summarizes the key structures and functions of the human eye. It describes the eyelid, tear film, cornea, aqueous humor, iris, lens, vitreous, retina, choroid, intraocular muscles, optic nerve and their roles in vision. The tear film lubricates the eye and the cornea refracts light, while the iris controls the pupil size. The lens focuses light and the retina converts it to neural signals. Various muscles control eye movement and the optic nerve transmits signals to the brain.

1. Ocular Anatomy
A Vision Teacher ‘s Guide

2. The Human Eye

3. Eyelid
• In addition to tear spreading, the
eyelid is primarily responsible for
corneal nutrition
• Also provides protection to
cornea
• Lashes offer additional protection

5. 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

6. Lacrimal System

7. Cornea
• Made up of 5 layers
• 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

9. Aqueous humor
• Fills space between cornea and iris
• Continuously produced by ciliary body
• Flows into 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

11. Limbus
• Juncture 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)

13. 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.

15. Sclera
• Whites of the eye
• Made up of 3 layers
• Tough, fibrous tissue: site of
extra-ocular muscle attachment
• Opaque...allows no light to enter
• Subject to inflammation

17. 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 per se

19. 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

21. 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

23. Zonules
• Attach the lens to the ciliary body
• May become broken or stretched
causing the lens to move out-of-
place

25. 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 disk 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

27. Choroid
• A brown vascular sheet lying
between the sclera and the retina
• This is the blood supply for the
retina

29. 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
• Actually an extension of brain tissue
• 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

31. 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

33. 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

35. 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 disk ratio is evaluation as a
measure of health…increase in size of cup
may indicate elevated pressure

37. Optic Nerve Pathways/Visual
Cortex
• Message is carried down the optic nerve
through pathways to occipital cortex; here
vision becomes sight
• At the optic chiasm, 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
• When damage is located anterior of the optic
chiasm; it is likely there will be a cortical
component to the field loss