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From Wikipedia, the free encyclopedia
The optic nerve comprises axons that emerge from the retina of the eye
and carry visual information to the primary visual nuclei, most of
which is relayed to the occipital cortex of the brain to be processed
Inflammation of the optic nerve causes loss of vision usually because
of the swelling and destruction of the myelin sheath covering the optic
nerve. Direct axonal damage may also play a role in nerve destruction
in many cases.
The most common etiology is multiple sclerosis. Up to 50% of patients
with MS will develop an episode of optic neuritis, and 20-30% of the
time optic neuritis is the presenting sign of MS. The presence of
demyelinating white matter lesions on brain MRI at the time of
presentation of optic neuritis is the strongest predictor for
developing clinically definite MS.
Almost half of the patients with optic neuritis have white matter
lesions consistent with multiple sclerosis. At five years follow-up,
the overall risk of developing MS is 30%, with or without MRI lesions.
Patients with a normal MRI still develop MS (16%), but at a lower rate
compared to those patients with three or more MRI lesions (51%). From
the other perspective, however, almost half (44%) of patients with any
demyelinating lesions on MRI at presentation will not have developed MS
ten years later.
Some other causes of optic neuritis include infection (e.g. Syphilis,
Lyme disease, herpes zoster), autoimmune disorders (e.g. lupus),
Inflammatory Bowel Disease, drug induced (e.g. chloramphenicol,
Ethambutol) vasculitis and diabetes
Major symptoms are sudden loss of vision (partial or complete), or
sudden blurred or "foggy" vision, and pain on movement of the affected
eye. Many patients with optic neuritis may lose some of their color
vision in the affected eye (especially red), with colors appearing
subtly washed out compared to the other eye.
A study found that 92.2% of patients experienced pain, which actually
preceded the visual loss in 39.5% of cases.
On medical examination the head of the optic nerve can easily be
visualised by an ophthalmoscope; however frequently there is no
abnormal appearance of the nerve head in optic neuritis, though it may
be swollen in some patients.
In many cases, only one eye is affected and patients may not be aware
of the loss of color vision until the doctor asks them to close or
cover the healthy eye.
Example of how optic neuritis affected one eye of a patient with
multiple sclerosisEpidemiologyOptic neuritis typically affects young
adults ranging from 18–45 years of age, with a mean age of
30–35 years. There is a strong female predominance. The
incidence is approximately 5/100,000, with a prevalence estimated to be
Treatment and prognosis
In most cases, visual functions return to near normal within eight to
ten weeks, but they may also advance to a complete and permanent state
of visual loss. Therefore, systemic intravenous treatment with
corticosteroids, which may quicken the healing of the optic nerve, is
often recommended, but it does not have a significant effect on the
visual acuity at one year, when compared against placebo.
Intravenous corticosteroids have also been found to reduce the risk of
developing MS in the following two years in those patients who have MRI
lesions; but this effect disappears by the third year of follow up.
Paradoxically it has been demonstrated that oral administration of
corticosteroids in this situation may lead to more recurrent attacks
than in non-treated patients (though oral steroids are generally
prescribed after the intravenous course, to wean the patient off the
medication). This effect of corticosteroids seems to be limited to
optic neuritis and has not been observed in other diseases treated with
Very occasionally, if there is concomitant increased intracranial
pressure the sheath around the optic nerve may be cut to decrease the
When optic neuritis is associated with MRI lesions suggestive of
multiple sclerosis (MS) then general immunosuppressive therapy for MS
is most often prescribed (IV methylprednisolone may shorten attacks;
initial only oral prednisone may increase relapse rate).
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