What is optic neuritis?
Optic neuritis is the medical term used to describe an “inflammation” of the optic nerve. The optic nerve allows us to see by carrying images from the eye to the brain. The optic nerve is like a bundle of electrical wires, and consists of about 1,200,000 separate tiny wires or nerve fibers. Each wire carries a part of the visual information we see to the brain. If some or all of the nerve fibers become inflamed and do not function properly, blurred vision results.
With optic neuritis, the nerve tissue becomes swollen and the nerve fibers do not work properly. If many of the nerve fibers are involved, vision may be very poor. However, if the optic neuritis is mild, vision is nearly normal.
What causes optic neuritis?
Various diseases and conditions may cause optic neuritis. In some people, optic neuritis is part of multiple sclerosis, a disease that affects many parts of the nervous system: In others, especially children, optic neuritis develops following a viral illness such as mumps, measles, or colds. Disabling neurologic disease is uncommon following isolated optic neuritis.
What are the symptoms and signs of optic neuritis?
Optic neuritis usually occurs suddenly. You may notice some or all of the following symptoms: blurred vision in one or both eyes (especially after exercising or a hot bath), vision is dim, as if the lights are turned down, colors appear dull or faded, and possibly the experience of pain behind the eye, particularly when moving the eyes.
A careful description of these symptoms is important to your ophthalmologist in the diagnosis of optic neuritis. Your doctor will perform a complete medical eye examination. By looking in the eye with an instrument called an ophthalmoscope, your ophthalmologist looks for swelling of the optic nerve where it enters the back of the eye. If the optic neuritis is not affecting the optic nerve very near the eyeball, the nerve may appear normal. After several weeks, the optic nerve may become pale.
Since optic neuritis can be confused with many other causes of poor vision, an accurate medical diagnosis is important: Other tests which may be performed include color vision, visual field, the reaction of the pupil to light, and MRI scanning. If a cause can be found and treated, further damage may be prevented.
How is optic neuritis treated?
Fortunately, most people recover normal vision with or without treatment. Although some people may have permanent visual defects from optic neuritis, these are usually mild. Research has shown that corticosteroids taken only by mouth are not beneficial in the treatment of optic neuritis, and may actually be harmful. However, treatment with high doses of intravenous corticosteroids followed by oral steroids may be beneficial in restoring vision more rapidly and in delaying symptoms of multiple sclerosis. Optic neuritis may recur in the same eye or it may appear for the first time in the other.