Webster's New World Medical Dictionary

optic nerve pathways
The course of the chemi-
cal and electrical impulse from light stimulating the
retina as it passes from the optic nerve to the vision
center of the brain. The left and right branches of
the optic nerves join behind the eyes, just in front of
the pituitary gland, to form a cross-shaped structure
called the optic chiasma. Within the optic chiasma,
some of the nerve fibers cross. The fibers from the
nasal (inside) half of each retina cross over, but
those from the temporal (outside) half do not.
Specifically, the fibers from the nasal half of the left
eye and the temporal half of the right eye form the
right optic tract; and the fibers from the nasal half of
the right eye and the temporal half of the left form
the left optic tract. The nerve fibers then continue
along in the optic tracts. Just before they reach the
thalamus of the brain, a few of the nerve fibers leave
to enter nerve nuclei that function in visual reflexes.
Most of the nerve fibers enter the thalamus, forming
a junction (synapse) in the back of the thalamus.
From there the visual impulses enter nerve pathways
called the optic radiations, which lead to the visual
(sight) cortex of the occipital (back) lobes of the
brain.
optic neuroma
A rare benign tumor of the optic
nerve.
optician
A specialist in fitting eyeglasses and
making lenses to correct vision problems. An
optometrist performs eye examinations and writes
prescriptions for corrective lenses; an optician fills
that prescription.
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optometrist
A practitioner who provides primary
eye and vision care, performs eye examinations to
detect vision problems, and prescribes corrective
lenses to correct those problems. Some optometrists
also make and fit eyeglasses, but many leave that job
to opticians. An optometrist is a doctor of optometry
(OD), not an MD. When an optometrist detects eye
disease, the patient may be referred instead to an
ophthalmologist, a physician who specializes in eval-
uating and treating diseases of the eye.