News — In the last month, researchers have taken an exciting step forward in identifying the genes that cause or increase the risk for age-related macular degeneration (AMD), a leading cause of blindness in the elderly.
AMD is a progressive disease that destroys central vision, making driving, reading, writing and recognizing faces difficult. There is no known cure for this disease which affects some 15 million Americans " a number that is expected to explode as "baby boomers" enter their golden years.
Three studies conducted independently of one another have linked a single gene variation that increases the risk of developing AMD by at least three-fold. Together, the three studies calculate that the mutation may account for anywhere from 20 percent to 60 percent of all AMD. The studies, reported in the March issue of the journal Science, were conducted by researchers at the University of Texas Southwestern in Dallas, Boston University and Sequenom, a biotech firm; Duke and Vanderbilt Universities; and Rockefeller and Yale Universities and the National Eye Institute.
Researchers have long suspected a genetic role in the disease, but until now they had only been able to narrow the search to one region of a chromosome. The results of these studies have significantly narrowed the range of chromosomal locations where researchers expect to find genes associated with AMD. Once AMD genes are found, researchers are hopeful that diagnostic tools can be developed for the disease.
"These findings are significant. A few studies have identified some genetic markers, but nothing with anything close to this frequency," said Academy spokesman Paul Sternberg Jr., MD, a retina specialist and George W. Hale professor and chairman of ophthalmology and visual sciences at Vanderbilt University Medical Center. "They provide some interesting insight into the factors that contribute to AMD, and it provides a definitive direction for identifying new treatments, but it does not yet give us a screening test for AMD, or a cure."
Another study also published in March provides additional information about the heritability of advanced AMD. Based on this study of 840 sets of twins " perhaps the largest twin study of AMD " researchers have shown genetic factor play a substantial role in the cause of AMD, explaining 46 percent to 71 percent of the variation in the overall severity of the disease. It also showed environmental factors unique to each twin contribute to the occurrence of AMD. This study was conducted by researchers at Harvard University, and published in the March issue of Archives of Ophthalmology.
While scientists believe there is a strong genetic component to AMD, most believe the cause will be found in the interplay of several genes combined with environmental factors, such as smoking and diet. Promising clinical trials have shown dietary supplements may reduce the risk of AMD.
In addition, researchers are working on medicines that stop the growth of new blood vessels. Such drugs could be used to treat wet AMD, and perhaps stop dry AMD from getting worse.
In the meantime, low vision/visual rehabilitation specialists can help blind or partially sighted patients make the most of their remaining vision. The Academy recently launched a vision rehabilitation initiative called SmartSight (www.aao.org/smartsight) that offers tips, tools, techniques and resources designed to help low-vision patients develop new ways of doing everyday activities.
The American Academy of Ophthalmology is the world's largest association of eye physicians and surgeons—Eye M.D.s—with more than 27,000 members. For more information about eye health care, visit the Academy's partner Web site, the Medem Network, at . To find an Eye M.D. in your area, visit the Academy's Web site at .
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