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Optic
Nerve
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Optic Nerve
Composed of nerve fibers that carry visual
information from the retina to the brain. Optic nerve damage causes a
loss of vision.
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Optic Nerve Hypoplasia
(see article on
Optic Nerve Hypoplasia)
A small and underdeveloped optic nerve. Optic
nerve hypoplasia is one of the leading causes of vision loss and
blindness in infants and children. Optic nerve hypoplasia occurs in the
early stages of fetal development, when the eyes are forming. The optic
nerve never fully develops or, once developed, dies-off and reduces in
size for unknown reasons. Recent evidence suggests that ganglion cell
axons, that make-up the optic nerve, are not able to grow through the
optic nerve head because certain chemical messengers are not present for
directional growth from the eye to the brain. Optic nerve hypoplasia is
variable, and can result in only minor vision problems to complete
blindness. Usually, if the infant has nystagmus the optic nerve
hypoplasia is more severe and vision is very much reduced. If the infant
does not have nystagmus, the likelihood for significant vision loss in
less. All infants with optic nerve hypoplasia should have a CT scan or
MRI to look for midline brain defects that can result in body growth
problems. If the infant does not have nystagmus, the chance of midline
brain defects is small. If the infant has nystagmus, the chance of
midline defects is greater. Some infants have optic nerve hypoplasia in
one eye only. If only in one eye, the chance of midline defects is very
small and the doctor may chose not to do a CT scan or MRI, depending on
other factors. There is no treatment or cure for optic nerve hypoplasia.
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Optic Nerve
Neuritis
An inflammation of the optic nerve usually
with some loss of sight (may be temporary). It may signify a more
serious neurological condition. A leading cause of optic neuritis is
multiple sclerosis (MS).
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Optic Nerve Disc
The visible part of the optic nerve inside
the eye. The axons of the ganglion cells of the inner retina make-up the
optic nerve (along with blood vessels as well as
nerves coming from the brain to the eye).
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Optic Atrophy
A disease of the optic nerve in which the
nerve fibers carrying the electrical impulses from the eye to the brain
start to die off. In such cases the optic nerve has a pale or whitish
appearance compared to the normal pink color. Optic atrophy is
associated with poor reading vision and often the cause of legal
blindness. May be associated with a serious medical condition and
requires further medical examination to determine the cause of the
atrophy. Not reversible. See Q and A
Archives section about Optic atrophy. |
| Q. My friend has
drusen of the optic nerve. She
has been having regular headaches and is fatigued a lot. She is 34
years old and does not have a family history of genetic eye problems.
What can she do to help this condition? Nothing.
Drusen of the optic nerve are little whitish or translucent bodies of
various size that are in the nonmyelinated part of the optic nerve head.
Both eyes are usually affected. In general they are not associated
with any systemic or eye conditions, so your friend's headaches and
fatigue are probably unrelated. Typically, drusen of the optic nerve
cause no problems unless they're big and/or start to interfere with
blood flow or compress the optic nerve fibers (rare conditions). Their
size tends to increase with age. Since no one knows what causes drusen
of the optic nerve or how they occur, your friend can probably do
nothing to help the condition. |
| Q. Is there
anything to be done to reverse the
atrophy of the optic nerve which prompted the loss of sight in one
eye? Nothing
will reverse optic atrophy. If the condition/disease that caused the
optic atrophy is identified and corrected, if possible, then the optic
atrophy and associated vision loss may not worsen. Whenever a patient
is identified with optic atrophy, it is very important that the cause of
the atrophy be identified. Often, extensive laboratory tests and
imaging tests (MRI, CT scan) are used to help identify the reason for
the optic atrophy and associated loss of vision. Unfortunately,
particularly in infants and young children, the cause of the optic
atrophy is sometimes never identified. |
| Q.
what is papilladema (papilledema)?
Papilledema, also called chocked
disk, is a swelling (edema) of the optic nerve disk - that part of the
optic nerve that the eye doctor can see when looking in the back of the
eye. The optic nerve runs from the eye to the early visual centers of
the brain. Papilledema is usually caused by an increase in intracranial
pressure (pressure inside the head/brain), obstruction of the central
retinal vein or malignant hypertension. The presence of papilledema is
never a good sign and often requires extensive testing to determine the
exact cause. Sometimes the cause of the papilledema is never found.
Also go to pseudo tumor
for more information. |
| Q. What is
the treatment for retro bulbous neuritis (retrobulbar
neuritis)?
Retrobulbar neuritis is an inflammation behind the eye of the
optic nerve. It is essentially an optic (nerve) neuritis which does not
show-up in the eye itself. Treatment depends on the cause of the optic
neuritis. However, in the majority cases the optic neuritis is
associated with multiple sclerosis (MS). The treatment for optic
neuritis is limited. |
| Q. What is a cresent (crescent)
scotoma? A scotoma is an area of reduced
vision in one or both eyes. A scotoma can take-on almost any
appearance, and the shape sometimes reflects the disease or cause of the
scotoma (see Simulations). In your case, the
scotoma is shaped like a crescent - something like a crescent of the
moon. It is likely off to the side - in your peripheral visual field.
A crescent scotoma is sometimes seen in retinal diseases. As a
rule-of-thumb, if you see the scotoma only in one eye then the cause of
the scotoma or disease process is within the affected eye (retina) or
along the early part of the optic nerve (before the optic chiasm) in the
affected eye. If the scotoma is present in both eyes and looks very
similar in each eye, then it is likely that the cause or disease process
is in the brain at the optic chiasm or further back along the visual
pathways. [Note: the optic chiasm is where the optic nerves from the
two eyes cross and, more or less, join together. Thus, anything that
happens to the visual system that occurs at or after the optic chiasm
almost always affects both eyes to more or less the same extent.
Conversely, anything that happens along the visual pathways before the
optic chiasm most likely affects one eye.] However, as the disease
process progresses, like in a retinal degeneration that affects both
eyes, eventually both eyes will become affected, even though the disease
process is at the retinal or eye level on the visual system. |
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W. R. Bryan Diabetic Eye Disease Research Fund
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