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Optic neuritis

Optic neuritis (or retrobulbar neuritis) is the inflammation of the optic nerve that may cause a complete or partial loss of vision. more...

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Causes

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 into vision.

Inflammation of the optic nerve causes loss of vision usually due to 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.

Some causes are viral-bacterial infections (e.g. herpes zoster), autoimmune disorders (e.g. lupus) and the inflammation of vessels (vasculitis) nourishing the optic nerve.

Optic neuritis can also emerge as an attendant, first, or sole manifestation of multiple sclerosis.

Symptoms

Major symptoms are sudden loss of vision (partial or complete) and occasionally pain on movement of the eyes. Most patients with optic neuritis may lose their color vision, as well.

On medical examination the head of the optic nerve can easily be visualised by an ophthalmoscope. 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.

Treatment and Prognosis

In most cases, visual functions return to near normal within 8 to 10 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, prevent complete loss of vision, and delay the onset of other multiple sclerosis symptoms, is often recommended. 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 corticosteroids.

Very occasionally, if there is concomittant increased intracranial pressure the sheath around the optic nerve may be cut to decrease the pressure.

When optic neuritis is associated with MRI lesions suggestive of multiple scelrosis (MS) then general immunosuppressive therapy for MS is most often prescribed.

Diagnosis

Optic neuritis is often diagnosed by the neurologist and managed by an ophthalmologist. However, ideally, a neuro-ophthalmologist should be consulted at a major university hospital center.

Read more at Wikipedia.org


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Steroid injections for eye ailment slow MS - steroid shots for optic neuritis delays onset of multiple sclerosis
From Science News, 12/11/93 by Elizabeth Pennisi

A reanalysis of a study that evaluated the use of steroids to treat inflamed optic nerves provides evidence that corticosteroid injections may delay the onset of multiple sclerosis (MS).

A chameleon among diseases, MS defies both understanding and treatment. This disorder can begin and progress erratically It is linked to the appearance of patches in the brain where myelin, the nerve cells' protective sheath, has disintegrated. Physicians can treat symptoms, but rarely can they slow the disease's progression (SN: 3/27/93, p. 197).

A diagnosis requires the separate development of two neurological problems, such as memory loss, tremors, vision problems, or partial paralysis. Recently. scientists have begun to use magnetic resonance imaging (MRI) to track the progression of this disease.

One of these neurological problems, optic neuritis, leads to sudden temporary loss or impairment of vision. Between 35 and 75 percent of those with optic neuritis later develop MS, says Donald H. Silberberg of the Hospital of the University of Pennsylvania in Philadelphia. At other times, the optic nerve becomes inflamed for different reasons.

From 1988 to 1991, 15 medical centers treated about 450 people diagnosed with their first case of optic neuritis. For two weeks, the participants got either steroid shots for three days and then pills, steroid pills alone, or pills containing no medication. The study revealed that injected steroids, followed by pills, provided marginal long-term benefit, says Roy W. Beck, an ophthalmologist at the Jaeb Center for Health Research, Inc. in Tampa, Fla. Those receiving injections simply recovered their sight a week or so faster than those who took pills. Eventually, all groups recovered equally well, a result suggesting steroids were unnecessary

That advice may now change. The researchers have gone back and determined how many of the people who showed no signs of MS at the time they received treatment later developed this disease. "We wanted to look at indicators of risk for MS," says Beck, who headed the research project.

To their surprise, about 7.5 percent of the 135 people who got shots and pills developed MS, while 14.7 percent of the 129 patients who took steroid pills only and 16.7 percent of the 126 who took pills with no medication got MS within two years, the group reports in the Dec. 9 NEW ENGLAND JOURNAL OF MEDICINE.

However, after two years, even those who received steroid shots began developing MS at the same rate as those in the other study groups, Beck says. He and his colleagues suspect that the shots present the immune system with a high enough dose of steroids to somehow counter the initial inflammatory response and curtail damage. This effect eventually wears off, however.

Some doctors already treat their MS patients with steroids, and a few small studies show that steroids can speed an MS patient's recovery from a flare-up of the disease, Beck says. "Our findings are at least supportive of this use."

Each participant received an MRI brain scan at the beginning of the study. The eye-study data confirm that these scans can help identify those at risk of developing MS, says Beck. Almost 25 percent of participants with abnormal scans had MS within two years, while just 5 percent of those with normal scans did. The more abnormal the scan, the more likely the development of MS.

"[The report] supports treatment with intravenous steroids, particularly [in] people with optic neuritis and abnormal MRI [scans]," comments Stephen C. Reingold of the National Multiple Sclerosis Society in New York City.

However, both Reingold and Silberberg caution that this study was not designed to assess a treatment for MS. Because patients knew when they received injections, the results could be biased, they warn. Also, the number of MS patients in each group was relatively small.

COPYRIGHT 1993 Science Service, Inc.
COPYRIGHT 2004 Gale Group

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