Blacks' high glaucoma risk is verified.

A study of 5,300 Baltimore residents has confirmed that glaucoma -- already considered the leading cause of blindness among U.S. blacks -- is five times more likely to afflict blacks than whites. The survey also revealed that the disorder strikes blacks earlier and independent of socioeconomic status or access to health care.

Though other studies have suggested that blacks might be more susceptible to glaucoma, this survey of a racially mixed population enabled investigators for the first time to compare blacks and whites in specific age groups and to confirm race-related differences, notes Maurice F. Rabb, medical director for the National Society to Prevent Blindness, in Schaumburg, Ill.

James M. Tielsch, Alfred Sommer and their colleagues at Johns Hopkins University in Baltimore set up five local screening clinics and invited 6,850 poor and middle-class black and white residents over age 40 to have their eyes checked. Of 2,913 whites and 2,395 blacks who underwent extensive eye tests and personal interviews between 1985 and 1988 1,770 showed vision or eye problems. During a follow-up screening of these patients at Hopkins, ophthalmologists diagnosed the optic-nerve damage that characterizes primary open-angle glaucoma in 100 blacks and 32 whites.

By age 70, one in 10 blacks -- compared with one in 50 whites -- develop this disease, the researchers report in the July 17 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION. In glaucoma, optic-nerve damage -- from increased pressure in the eye -- leads to failing vision, which can go unnoticed during its early stages.

"We now know that what was circumstantial evidence in the past is really well documented," says Carl Kupfer, director of the National Eye Institute in Bethesda, Md., which funded the study. "People in this [geographic] area are very comparable; we can eliminate [socioeconomic] factors."

About equal numbers of blacks and whites with glaucoma said they had their eyes examined during the past year and about ahlf of those diagnosed with the disease said they did not know they had developed it until they participated in the survey. Sommer therefore concludes that lack of access to health care cannot account for the racial differences.

Overall, the Baltimore Eye Survey found that in the 40- to 49-year-old age group, 1.23 percent of blacks get glaucoma, compared with 0.92 percent of whites. By age 80, that percentage rises to 11.26 percent of blacks, but just 2.16 percent of whites. Sommer estimates that primary open-angle glaucoma affects 1.6 million U.S. residents over 40. However, doctors can treat the condition to slow or stop vision loss.

The new survey results further emphasize the need for people over age 40, especially blacks, to undergo periodic comprehensive eye exams, vision experts say. Adds Kupfer, "It is likely that increasing awareness of glaucoma in the black community could have a major impact on preventing blindness from this disease."