TUESDAY, April 24, 2007 (HealthDay News) -- Two genes could determine an older person's vulnerability to an advanced form of age-related macular degeneration (AMD), researchers report.
People who smoked or were overweight faced an even greater risk for the potentially blinding eye condition, the study found.
"The two genetic variants are related and predict to a certain extent which individuals who have earlier-intermediate forms of macular degeneration progress to the advanced form and visual loss," explained the study's lead author, Dr. Johanna M. Seddon, director of the Ophthalmic, Epidemiology and Genetics Service in the department of ophthalmology at Tufts-New England Medical Center and New England Eye Center.
"Genetic variants are part of the way we can differentiate who gets worse, coupled with environmental factors like a high body mass index and smoking," said Seddon, whose team published its results in the April 25 issue of the Journal of the American Medical Association.
The findings have implications for the prevention of AMD, one expert said.
"They've actually identified specific genes and specific abnormalities in specific genes that prove that macular degeneration has a strong genetic component," said Dr. Robert Cykiert, clinical associate professor of ophthalmology at New York University School of Medicine in New York City. "What this says is if you have someone in your immediate family such as parents or siblings with AMD, then you need to see an ophthalmologist and be carefully followed, because there are things that can be done to prevent progression."
Down the line, there may even be a blood test to detect these genes, further brightening the picture for prevention and early treatment, Cykiert said.
But it's too early to recommend widespread screening, the authors stated.
"Some individuals who progress do not have these genetic variants or have never smoked," Seddon said. "We need to refine this predictive measure, add more genetic variants and maybe even more environmental factors."
Age-related macular degeneration (AMD) involves damage to the inner lining of the eye and can lead to visual impairment and even legal blindness.
"There are several million people who have the earlier-intermediate stages of AMD once they reach the age of 75 or older, but [only] 6 to 8 percent of individuals have advanced disease, so the question is, how do we predict or identify those people who are at higher risk?" Seddon said.
AMD has previously been associated with variations in two genes: CFH and LOC387715. But previous studies exploring this relationship had been cross-sectional in nature, not prospective as the current one is.
For this study, Seddon and her colleagues looked at almost 1,500 white adults aged 55 to 80 with the earlier intermediate signs of macular degeneration. During an average of more than six years of follow-up, 281 individuals progressed to advanced AMD in one or both eyes.
Genotypic analysis revealed that two specific genetic polymorphisms -- CFH Y402H and LOC387715 A69S -- were linked with progression to more advanced AMD.
The risk of progression was 2.6 times higher for those with the CFH variant and 4.1 times higher for those with the LOC387715 variant, after controlling for other factors.
For people who had one of the genotypes, smoking and being overweight increased the risk 19-fold, making a strong argument for lifestyle changes in people who are identified as having the genetic risk factors.
More information
For more on AMD, visit the U.S. National Eye Institute.
