What is Optic Neuritis?

Optic neuritis is an inflammation of the optic nerve that often occurs in people who have multiple sclerosis (MS). This inflammatory disease also can be triggered by infection or occur as a standalone condition with no discernible underlying cause. Common symptoms of this disease include eye pain and loss of vision. Most people who suffer an isolated episode of optic nerve inflammation recover their vision. Sometimes, though, the vision loss is permanent.

Optic neuritis usually develops as a result of an autoimmune disorder. This type of disorder is a dysfunction of the immune system. A normal, healthy immune system can distinguish between body tissues and foreign cells and tissues, and it will attack only those that are foreign. When an autoimmune disease develops, the immune system becomes sensitized to attack one or more of the body’s own proteins.

In most cases, the autoimmune disorder that triggers optic nerve inflammation is multiple sclerosis. This disease develops when the immune system begins to attack cells that produce a protein called myelin. This protein is present on the surface of most nerve cells, and immune system destruction of myelin leads to progressive inflammation and damage to the spinal cord and brain nerves. It is believed that optic nerve inflammation causes eye disease in the same way.

Optic neuritis is often one of the first symptoms of MS, particularly in women. Long-term studies of people with optic neuritis indicate that of women who present with optic nerve inflammation, up to 75 percent eventually will develop multiple sclerosis. Overall, someone with this eye inflammation has approximately a 20 percent chance of subsequently developing multiple sclerosis. Even so, this disease is not always a predictor of MS, because bacterial sinus infection, bacterial eye infection or systemic viral infections can trigger this type of eye inflammation.

The most common symptom of optic neuritis is a loss of vision — typically in one eye — that develops over several hours and can be accompanied by eye pain. Other symptoms of optic neuritis include loss of color vision, pain when the eyeball is moved and changes in the way the pupil of the eye responds to light. When vision loss occurs as an isolated incident, without an underlying cause such as multiple sclerosis, most people have a good chance of regaining their lost vision within a few weeks.

If vision loss and other symptoms are because of multiple sclerosis, the eye inflammation is likely to recur, and the chance of regaining vision is lower with each successive episode. Treatment with intravenous corticosteroids to reduce inflammation can help improve the chances that vision will return to normal, or at least that vision loss can be minimized. Steroid treatment must be of short duration, however, because of the possibility of complications from systemic steroid use.