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Welcome to 2 minute neuroscience, where I explain neuroscience topics in 2 minutes or
less.
In this installment I will discuss the optic nerve.
The optic nerve is a sensory nerve responsible for transmitting information about vision
to the brain.
The nerve begins in the retina as the axons of cells called retinal ganglion cells.
These axons come together to leave the eye at a region called the optic disc and form
the optic nerve.
The optic nerve leaves the eye and extends to a structure called the optic chiasm where
it meets the optic nerve from the other eye.
At the optic chiasm, the optic nerve fibers carrying information from the sides of the
retina closest to the nose cross over to the other side of the brain, while those carrying
information from the sides of the retina closest to the temples remain on the side of the brain
where they are.
After leaving the optic chiasm, the nerve fibers are referred to as the optic tract.
Most of the nerve fibers in the optic tract end in the lateral geniculate nucleus of the
thalamus, and from there the information will be passed on to the visual cortex.
Damage to the optic nerve can occur due to a variety of causes like trauma, tumors, stroke,
or glaucoma.
The deficit that occurs after damage depends on where the nerve is damaged, and involves
some degree of visual defect or anopsia.
If the damage occurs before the optic chiasm, then the patient will experience blindness
in the eye supplied by that optic nerve.
Damage to the middle of the optic chiasm will cause loss of the lateral visual field of
both eyes, due to the way fibers from the nasal side of the retina cross over at this
point.
If the optic tract is damaged, one half of the visual field will be lost in both eyes.