The retina lies in the back of the eye and is a multi-layered tissue which detects visual images. These images are transmitted to the brain through approximately 1 million tiny nerve fibers. These nerve fibers converge in the back of the eye, before going to the brain, into a bundle called the optic nerve. If some or all of the nerve fibers are damaged, visual capability deteriorates.
When the optic nerve becomes inflamed, this condition is called optic neuritis. The nerve tissue becomes swollen and red, and the nerve fibers do not work properly. If many of the nerve fibers are involved, the vision may be dramatically affected, but if the optic neuritis is mild, vision is nearly normal. Optic neuritis can be caused by many diseases and conditions and may affect the optic nerve of one or both eyes.
Some people, especially children, develop optic neuritis following a virus illness such as mumps, measles, or a cold. In others, optic neuritis may occur as a sign of a neurologic disease affecting nerves in various parts of the body, such as multiple sclerosis. In a rare condition called Leber’s optic neuropathy, which often runs in families, a special kind of optic neuritis may appear in both eyes within a short span of time. Most of the time, however, the cause for optic neuritis is unknown. In those cases, the eye disorder is called neuritis idiopathic, meaning that no particular cause can be found.
Optic neuritis usually comes on suddenly, and the patient notices vision is blurred in one or both eyes. The vision is dim, like somebody turned down the lights, and colors may appear to be washed out. There may be pain in the area of the eye socket, especially when moving the eyes. The vision may continue to get worse over a week or two, and may seem worse after exercising or a hot bath.
A careful description of these symptoms is important to your doctor for the diagnosis of optic neuritis. The optic nerve enters the back of the eye where it appears as a small disc. Your eye doctor can examine the optic nerve inside the eye by using a special instrument called an ophthalmoscope. Swelling of the optic nerve may or may not be visible. If the optic nerve inflammation occurs inside the eye, it can be readily detected. If swelling of the nerve occurs behind the eye, the doctor may not be able to see the swollen nerve tissue.
Since optic neuritis can be confused with many other causes of poor vision, an accurate medical diagnosis is important. Ultrasound, CT scans or visual brain wave recordings might be ordered. Other tests which may be performed include color vision, side vision, and pupil reactions to light.
Unfortunately, there is no good treatment for optic neuritis. Cortisone-like medications (steroids) can be prescribed, but in most cases they are not effective. In many cases, patients with optic neuritis improve without treatment. The vision may return to normal or, in some cases, good but incomplete improvement occurs. A few patients fail to recover normal vision, especially those with special conditions.