What is Optic Neuritis?
Optic neuritis is an inflammation of the optic nerve, the bundle of nerve fibers in your eye that transmits visual information to your brain. Optic neuritis usually develops due to an autoimmune disorder that may be triggered by a viral infection. In some people, signs and symptoms of optic neuritis may be an indication of multiple sclerosis, a condition resulting in inflammation and damage to nerves in your brain and spinal cord. In 15 to 20 percent of people who eventually develop multiple sclerosis, optic neuritis is their first symptom. Most people who experience a single episode of optic neuritis eventually recover their vision. Treatment with steroid medications may speed up vision recovery.
What are the symptoms of Optic Neuritis?
Optic neuritis usually affects one eye, although it may occur in both eyes simultaneously. Most people who develop optic neuritis experience eye pain that's worsened by eye movement. Pain associated with optic neuritis usually peaks within one week and then goes away within several days. The extent of visual loss associated with optic neuritis varies. Some people experience severe difficulty seeing, while others might not notice any changes in their vision. Vision loss, should it occur, usually develops over the course of a day to two weeks and may be worsened by heat or exercise. Vision loss is usually temporary, but it may be permanent in some cases. Optic neuritis often affects the perception of colors. You may notice that the colors of objects, particularly red ones, temporarily appear "washed out" or less vivid than normal.
Optic neuritis is frequently associated with autoimmune disorders, including multiple sclerosis and neuromyelitis optica. Other causes of optic neuritis include infections (Lyme disease, hepatitis B, herpes, etc.), diabetes, cranial arteritis, and drugs (for instance, ethambutol (Myambutol), which is used to treat tuberculosis, has been associated with the development of optic neuritis). Optic neurititis most often affects young adults ages 20 to 45 years. The average age of onset is about 30 years. Older people or children also can develop optic neuritis, but it occurs less frequently in these groups. Women are twice as likely to develop optic neuritis. Optic neuritis occurs more in whites.
Vision loss may persist after optic neuritis has improved. Up to 10 percent of people with a history of optic neuritis have some degree of long-term vision loss. Most people have some permanent optic nerve damage following an episode of optic neuritis, but they may not experience any symptoms.
How is Optic Neuritis diagnosed?
You will need to see an ophthalmologist for a definitive diagnosis. He or she will check your vision and your perception of different colors. During ophthalmoscopy, your doctor shines a bright light into your eye and examines the structures at the back of your eye. This eye test evaluates the optic disk, which is the area where the optic nerve enters the retina in your eye. The optic disk becomes swollen in about one-third of people with optic neuritis. In the pupillary light reaction test, your doctor may swing a flashlight in front of your eyes to see how your pupils respond when they're exposed to bright light. Pupils affected by optic neuritis don't constrict as much as healthy eyes do when stimulated by light. Other tests to diagnose optic neuritis may include a MRI scan and blood tests.
How is Optic Neuritis treated?
Optic neuritis usually gets better on its own. In some cases, steroid medications are used to treat optic neuritis, because they help reduce inflammation in the optic nerve. In instances in which steroid therapy has failed and severe vision loss persists, a treatment called plasma exchange therapy may help some people recover their vision.
The prognosis following optic neuritis is generally good. Most people regain close to normal vision within six months after an episode of optic neuritis. If you have optic neuritis and you're at high risk of developing multiple sclerosis, and additional medical treatment is necessary. People with multiple sclerosis or neuromyelitis optica may experience recurrent attacks of optic neuritis sometime after they've recovered from the initial episode.