African Americans, at high risk for glaucoma, can reduce incidence by nearly half with regular use of medication, a study shows.

African Americans have a substantially higher risk of developing glaucoma than do whites, but researchers have now found they respond just as well to preventive therapy.

A major study released two years ago showed that the regular use of prescription eyedrops by whites at risk of developing the eye disorder can reduce its incidence by nearly 50%, but results in blacks were not as clear. 

Now a follow-up study has shown that the drops produce a similar reduction among blacks, even though they have two to three times the incidence of glaucoma as whites and often develop it at a younger age.

"It's important because it for the first time demonstrates that a group of people who are at high risk to develop glaucoma - people of African American descent - are also likely to benefit from preventive measures," said Dr. Richard Parrish of the University of Miami, a coauthor of the paper.

A second study has found that cholesterol-lowering medications - such as the family of drugs known as statins - can also reduce the risk of glaucoma.

Glaucoma is one of the most common causes of vision loss in Americans and is the leading cause among African Americans. It affects an estimated 2.2 million Americans over the age of 40, half of whom do not know they have it. 

Blindness results primarily from damage to the optic nerve caused by a buildup of pressure in the eye. The pressure occurs when fluid flows into the eye faster than it flows out. Symptoms begin with the loss of peripheral vision, and the visual field narrows until blindness is total.

The most common risk factors include high ocular pressure, age, a family history of glaucoma and diabetes.

The eyedrops study, led by Dr. Eve Higginbotham of the University of Maryland Medical Center, enrolled 408 blacks, ages 40 to 80, who had elevated eye pressure but no signs of glaucoma. Half were randomly chosen to receive eyedrops - the study used six different classes of pressure-reducing drugs - and half were simply monitored.

The team reports in the current Archives of Ophthalmology that use of the medication reduced eye pressure by about 20%. At the end of seven years, only 8.4% of those who received medication had developed glaucoma, compared with 16.1% of those who did not. 

Among the 1,200 patients of other races, more than 4% of those who received medication developed glaucoma, compared with more than 11% of those who did not. 

The National Eye Institute recommends that blacks receive a dilated-eye examination every two years after age 40 and that everyone receive exams regularly after age 60. It is estimated that as many as 6 million Americans are at increased risk of developing glaucoma.

In the second study, published in the same journal, epidemiologist Gerald McGwin Jr. of the University of Alabama at Birmingham and his colleagues studied the records of 667 men older than 50 who had been diagnosed with glaucoma and compared them with 6,667 healthy men of the same age.

They concluded that men who had used any of the statin drugs for 24 months or longer had about a 40% reduction in risk for developing glaucoma. The statins are the most commonly prescribed drugs in the world and are widely used to prevent heart attacks and strokes.

They found a slightly smaller reduction in risk among men who had used other types of cholesterol-reducing drugs, suggesting that it is cholesterol-reduction rather than the statins that provides the major benefit.

The researchers cautioned that the findings were based on a retrospective study and need to be confirmed by a controlled trial.