Glaucoma More Likely in Blacks, Study Finds : Disease: Researchers speculate that genetic susceptibility, not health care, may be the reason.
Blacks are four to five times more likely than whites to develop one of the most common causes of preventable blindness in the United States, according to the first major study to explore in detail long-suspected racial differences in rates of glaucoma.
The study, published today in the Journal of the American Medical Assn., found that disparities in health care did not explain the racial gap. Instead, the researchers speculated that it may reflect “an underlying genetic susceptibility” to glaucoma.
“For the first time, we have pinned down without any question that glaucoma in blacks is not only more common . . . but also that it occurs at an earlier age,” said Dr. Carl Kupfer, director of the U.S. National Eye Institute, commenting on the study.
Kupfer and others said the finding underscores the importance of annual, comprehensive eye exams for many blacks 30 and older. His agency intends to launch a nationwide public education campaign later this year to call attention to glaucoma.
“When you start to see four- to six-fold increases in blindness from this disease in the initial black population, that’s extremely alarming,” said Dr. Edwin Marshall, associate professor of optometry at Indiana University. “I don’t think people can imagine that sort of difference.”
The precise causes of glaucoma are not known. But it occurs when abnormally high pressure of fluid in the eye causes damage to the optic nerve. About 1.6 million Americans over age 40 are believed to suffer from so-called primary, open-angle glaucoma, the most common form.
Glaucoma often sets in without easily detectable symptoms. It erodes peripheral vision, rather than central vision, so it may go unnoticed. Early damage can be detected through regular eye exams, but experts say some exams are insufficiently thorough.
Because the initial effects are subtle, many cases are missed until extensive damage has been done. Glaucoma can be treated effectively through drugs, laser treatment or surgery, but it is impossible to restore the vision that has been lost.
“What all this means is that we need to be much more careful and aggressive about trying to pick up glaucoma earlier among African-Americans than among white Americans,” said James M. Tielsch, a Johns Hopkins School of Medicine researcher and lead author of the paper.
Tielsch and others screened 2,395 blacks and 2,913 whites age 40 or older living in east Baltimore. They found that the racial gap was evident from the youngest ages and widened as the men and women aged.
Among men and women in their forties, the rate of glaucoma was less than one in 100 among whites and 1.23 in 100 among blacks--a finding researchers say is consistent with other observations that some blacks develop glaucoma even younger, in their 30s.
Among people in their 70s, blacks had a glaucoma rate of 9.15 per 100, compared to 2.89 among whites. Among men and women 80 and older, blacks had a rate of 11.26 per 100, compared to 2.16 among whites.
“We fundamentally thought it was likely that blacks were at higher risk but we didn’t understand the magnitude of the excess risk,” said Tielsch. “And we wanted to understand if there were potential explanations for this.”
It did not appear that inadequate access to, or use of, health care services could explain the difference. The researchers found that similar proportions of blacks and whites in the study reported having seen an eye specialist in the previous year.
“In addition, approximately half of all patients, both blacks and whites, were unaware they had glaucoma at the time our study diagnosis was made, and equivalent proportions of those affected were already receiving treatment,” they wrote.
“Our basic feeling is that it’s unlikely that access to, or effective utilization of, health care services can explain this difference,” Tielsch said in an interview. “The magnitude of the difference is just too big to be explained by that.”
Experts in the field said the new study is the first to examine glaucoma rates among similar groups of blacks and whites. They said past studies have looked only at one group--for example, whites in Wales or blacks in Jamaica.
In one such study, Dr. M. Roy Wilson of UCLA and the Charles R. Drew University of Medicine and Science found that approximately 8.8% of blacks in St. Lucia suffered from glaucoma. An earlier study in Jamaica found three to five times the rates seen in Wales.
However, Wilson said this week that the rate of glaucoma in Martinique appears to be relatively low--an observation he said suggests perhaps genetic differences among different groups of blacks from different parts of Africa.
Wilson, an assistant professor of ophthalmology at Jules Stein Eye Institute at UCLA and chief of ophthalmology at Drew, said a thorough eye exam for glaucoma must include not only a test of fluid pressure in the eye but also scrutiny of the optic nerve for damage.
Rates of Glaucoma
Glaucoma, a leading cause of preventable blindness, affects blacks at rates that are four to five times higher than those of whites, according to a recent study. Researchers believe the difference may result more from an underlying genetic susceptibility than from differences in use of health care. BLACKS
Age Number Screened Cases Adjusted Rate 40-49 632 6 1.23 50-59 699 25 4.05 60-69 614 31 5.51 70-79 349 27 9.15 Above 80 101 11 11.16 Total 2,395 100 4.74
WHITES
Age Number Screened Cases Adjusted Rate 40-49 543 1 .92 50-59 618 2 .41 60-69 915 7 .88 70-79 631 18 2.89 Above 80 206 4 2.16 Total 2,913 32 1.29
SOURCE: Journal of the American Medical Assn.
Compiled by Times researcher Michael Meyers
