Optic Neuritis (cont.)

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What causes optic neuritis?

The precise cause of optic neuritis is unknown, but it is thought to be a type of autoimmune disorder. The immune system is generally used to fight infection by creating a reaction that combats bacteria, viruses, fungi, and other foreign proteins. In autoimmune diseases, this reaction is mistakenly directed against a normal part of the body, creating inflammation and potential damage. In the case of optic neuritis, the optic nerve becomes swollen and its function is impaired. Inflammation and destruction of the protective myelin sheath that coats and insulates the optic nerve, plus direct damage to the nerve axons results in loss of vision.

Optic neuritis is frequently an indication of multiple sclerosis (MS), a disease in which the immune system attacks the myelin sheath covering nerve fibers in the brain and spinal cord, resulting in inflammation and nerve damage. Optic neuritis typically resolves initially, but recurs.

In 15%-20% of people who eventually develop multiple sclerosis, optic neuritis is their first symptom. The risk of developing multiple sclerosis following one episode of optic neuritis is approximately 50% within 15 years of the episode of optic neuritis. Studies vary, but between 27% and 70% of patients who have optic neuritis for the first time will have 2 or more MRI abnormalities consistent with MS. The 5-year risk of developing multiple sclerosis is 16% if the MRI is negative, 51% if there are 1 to 3 lesions.

Neuromyelitis optica is another autoimmune condition in which demyelination mainly occurs in the spinal cord and optic nerve, but is less noticeable in the brain. In this infrequent condition, the patient can experience weakness or paralysis in the limbs and/or bladder and bowel dysfunction, as well as loss of vision.

There are a variety of conditions that can affect the optic nerve causing symptoms similar to optic neuritis (optic neuropathies).

Infection, trauma, hereditary conditions, toxic or nutritional problems, compressive lesions, arteritis, diabetes, glaucoma, etc. Treatment of optic neuropathies associated with these patients depends on the cause, and is directed at the underlying disease.

Medically Reviewed by a Doctor on 1/21/2014

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