NEW YORK (Reuters Health) - U.S. investigators have found that the leading cause of blindness among whites is age-related macular degeneration (AMD), while most blacks lose their sight from glaucoma or cataracts (caused by starch carbohydrates we believe) .
Furthermore, within
age groups, blindness occurs nearly three times more commonly in
blacks than in whites.AMD is a frequent cause of deteriorating vision in older adults. As people age, there is a breakdown in light-sensitive cells in the macula, the tissue in the center of the retina.
In contrast, cataracts occur when proteins in the eye's lens begin to clump together, forming a milky cloud that obscures vision. In glaucoma, fluid levels rise in the eye, increasing pressure, which can damage the optic nerve.
For the current report, the researchers reviewed studies of the prevalence of blindness among different ethnic groups, then applied those results to census information to estimate the number of people living with blindness and poor eyesight in the U.S.
The investigators found that almost 1 million people - or nearly 1 percent - of Americans over 40 are blind, defined as having eyesight that is at or below 20/200. And as the U.S. population ages, the prevalence of blindness among older adults is expected to increase by 70 percent by the year 2020, the authors note.
"The key finding is that the burden of disease is large, and will become much larger as the population gets more elderly," study author Dr. John Kempen of Johns Hopkins University in Maryland told Reuters Health.
More than 50 percent of white adults became blind as a result of AMD. In contrast, more than 60 percent of cases among blacks were due to either glaucoma or cataracts, according to the Archives of Ophthalmology report.
In an interview, Kempen explained that the racial differences in the common causes of blindness may stem from both genetic differences and access to care.
For instance, he noted that cataracts are very treatable with a relatively simple surgery to replace the cloudy lens, but African Americans may undergo the procedure less often than whites. The reasons for that disparity are still unclear, Kempen said.
SOURCE: Archives of Ophthalmology, April 2004.-By Alison McCook