Blindness

August 18, 1999
Web posted at: 12:07 PM EDT (1607 GMT)

In this story: Description Risk Symptoms Treatment Prevention RELATEDS

From WebMD

DESCRIPTION

Blindness is more a matter of degree than all or none. For instance, a person can be considered "legally" blind for insurance and disability purposes, yet not actually have lost 100 percent of his or her vision. The Social Security Administration defines blindness as 20/200 vision or less in the better eye with the use of a corrective lens, or as a defect in which the widest diameter of the visual field is less than 20 degrees.

Estimates of the number of Americans who are legally blind varies. Rates range from 1/2 million to 1.3 million depending upon the source, and around 10 percent of those are completely sightless or have only the merest ability to perceive any light.

RISK

There are three main causes of blindness in the United States: 1. Macular degeneration. This is the leading cause of visual impairment among older people. It results from changes to the macula, the portion of the retina that is responsible for clear, sharp sight. Sometimes, the degeneration is simply part of the natural aging process, while other times it occurs when fluid from blood vessels leaks into the eye. 2. Diabetic retinopathy. This is the leading cause of new cases of blindness among young working adults. This condition occurs in one-third of diabetics who have had the disease for at least 10 years. Over time, diabetes can weaken and cause changes in the small blood vessels that nourish the retina, leading to the production of scar tissue. If untreated, diabetic retinopathy can cause blindness. 3. Glaucoma. About 3 million Americans have this condition. It is the leading cause of blindness among African-Americans. Glaucoma is a group of diseases in which the passages that allow fluid in the eye to drain become clogged, resulting in a fluid build-up, which increases pressure inside the eye and damages the optic nerve. Those most at risk are people who are over 40; who have a family history of the disease; who are African-American; or who are very nearsighted or diabetic.

There are many other, less-common causes of blindness, such as high blood pressure, Grave's Disease, sports injuries and other accidents.

SYMPTOMS

Symptoms vary, but in many cases include blurred vision and the loss of peripheral (side) vision.

In macular degeneration, a person can have a gradual loss of clear color vision and a dark or empty area in the center of the vision. In diabetic retinopathy, a person may notice cloudiness, blind spots or "floaters." And in glaucoma, symptoms can include the appearance of colored rings around lights and pain or redness.

TREATMENT

In general, the vision that has been lost cannot be restored. But treatment, including laser surgery or eyedrops, can prevent the progression of vision loss.

Breaking research shows that an experimental pill can prevent some cases of blindness by stopping the growth of abnormal blood vessels in the retina. And researchers recently found a gene that causes a form of glaucoma at a young age, which could lead to new developments in prevention and treatment.

Vision aids, such as the use of canes and guide dogs, along with special lenses, can improve a person's ability to function when sight is severely impaired.

PREVENTION

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