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Structure and Function of the
Eye
SPE 516
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The Bony Orbit
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The Muscles of the Eye
(Extraocular muscles)
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Superior and Inferior rectus
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Superior rectus
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Attached to the eye at 12 o’clock
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Moves the eye up.
 Inferior rectus
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Attached to the eye at 6 o’clock
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Moves the eye down.
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Lateral Rectus
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Lateral Rectus
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Also called the external rectus
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Attaches on the temporal side of the eye
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Moves the eye toward the outside of the head (toward the temple)
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Medial Rectus
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Medial Rectus
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Also called the internal rectus

Attached on the nasal side of the eye
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Moves the eye toward the middle of the head (toward the nose)
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Superior Oblique

Attached high on the temporal side of the eye.
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Passes under the Superior Rectus.

Moves the eye in a diagonal pattern -- down and in.

Travels through the trochlea
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Inferior Oblique
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Attached low on the nasal side of the eye.
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Passes over the Inferior Rectus.
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Moves the eye in a diagonal pattern -- up and out.
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The Nerves That Control the
Muscles of the Eye
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Third Cranial Nerves
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Fourth Cranial Nerves
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Sixth Cranial Nerves
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Lids and Lashes
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Main function is the protection of the eye.
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They also help to distribute tears which wash and lubricate the eyes.
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The Lacrimal System -- Tears
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The Refractive Structures
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These structures bend the light so that a clear image is produced.
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They are:
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tears
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conjunctiva
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cornea
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aqueous humor
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lens
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vitreous humor
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Chambers of the Eye
1. Anterior chamber – from cornea to iris
2. Posterior chamber – from iris to zonules and lens –
These two are responsible for the production and drainage of the aqueous
which is produced continuously throughout your life.
Aqueous is produced in the posterior chamber by the ciliary body travel
through the iris to drain out the anterior chamber (through the Canal of
Schlemn)
3. Vitreous – gel like –gives the eye its shape not produced – damage or
loss can cause retinas to fall or tear
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Layers of the eye
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Sclera and Cornea
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uveal tract
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Choroid
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Iris
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Ciliary body
retina
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Sclera and Cornea
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Form the outer layer of the eye – 1/6 cornea and 5/6 sclera

Cornea is clear- sclera is white (they transition at the limbus)
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Very tough and provide protection

Sclera maintains shape of the eye
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Cornea is the major refractor of the eye
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Uveal Tract
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Choroid – vascular layer, major supplier of nutrients and blood
supply to the eye
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Iris – Controls light that enters eye
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Cilliary body- produces aqueous humor to bathe lens and provide
nutrients to lens and cornea and provides accommodation.
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The Retina
The retina is made up of cones and rods

Rods -peripheral retina
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Motion, low light, no color
Cones -central retina
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Highly centralized in the fovea
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Color
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Fine detail
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The Optic Pathway
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Begins at the optic nerve.
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Impulses cross and partially split at the optic chiasm.
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After the chiasm, it becomes the optic tract.
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Lateral geniculate bodies (sensory way stations)
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Some fibers go to the colliculus (located in the mid brain)
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Optic Pathway (cont.)
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The other fibers fan out into the visual cortex which is located at the
top and back of the brain.
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Vision and the Brain
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Primary visual cortex (Striated Cortex) -
spatial organization of a scene
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shapes of objects
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brightness and shading of parts of objects
Secondary visual cortex (Prestriated Cortex) -
pattern recognition
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The Brain and Vision (cont)
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Temporal Lobes
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center for visual learning
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recognition by sight
Midbrain -- Limbic sector
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emotional responses to visual stimuli
Midbrain -- Superior Colliculus -
guides visual attention