Encyclopedia - Optic Neuritis

What causes optic neuritis?
What are the signs of optic neuritis?
What is the treatment for optic neuritis?

Optic neuritis is an inflammation of the optic nerve, which is the bundle of nerve fibers that starts at the back of the eye and carries light impulses from the retina to the brain (See Anatomy of the Eye). The retina receives light signals like the film in a camera, and the optic nerve transmits these signals to the brain where they are processed and turned into images, giving us the ability to see. If some or all of these nerve fibers become inflamed, the optic nerve becomes swollen and the fibers do not work properly, causing blurry vision. Depending on the number of inflamed nerve fibers, vision can range from near normal to extremely poor.

Optic neuritis is a relatively rare condition that can affect both adults and children. In adults, the condition usually affects one eye, while in children it often affects both eyes at the same time. The most common age for developing the condition is in the 30s, but it can affect people of all ages.

What causes optic neuritis?

Optic neuritis is usually associated with other medical problems, particularly viral infections and multiple sclerosis (MS). The disorder is often the first symptom of MS, and about 40 percent of people who experience optic neuritis eventually develop multiple sclerosis. The condition can also develop from an abuse of tobacco or alcohol, or from exposure to toxic substances such as lead or wood alcohol. Often the actual cause of optic neuritis cannot be determined.

What are the signs of optic neuritis?

Symptoms of optic neuritis usually come on suddenly and may include blurry or dim vision (as though the lights are being turned down) and a fading of colors. There can also be pain in the eye socket, impaired depth perception, and blind spots in the field of vision. Loss of vision usually occurs over a period of 2 to 5 days and generally improves within 4 to 12 weeks.

The condition can be difficult to diagnose because the symptoms are similar to those caused by several other eye problems. One of the first steps in diagnosing optic neuritis is an examination of the optic nerve with an instrument called an ophthalmoscope. The optic nerve enters the back of the eye and is visible to the doctor as a small disc. Any swelling of this inside part of the nerve can be detected, but if the swelling occurs behind the eye, it is not visible and other diagnostic procedures are necessary. These procedures may include tests such as an ultrasound, CT scans, or visual brain wave recordings. Other standard tests used in diagnosing optic neuritis are color vision, peripheral vision, and the reaction of the pupil to light.

What is the treatment for optic neuritis?

Unfortunately, there is no consistently reliable treatment for optic neuritis. Steroids such as cortisone and prednisone are sometimes prescribed, but their effectiveness in treating the problem is questionable. Most people who develop the condition, however, recover normal vision without treatment. Recovery may take from a few weeks to a few months, depending on the severity of the condition.