Age-related macular degeneration (AMD) is the leading cause of irreversible blindness among older individuals in many parts of the world. In the United States alone, about 10 million people have signs of AMD. The relative importance of genes and environment in the development of this major public health problem is not well understood.
Researchers led by Johanna M. Seddon, M.D., at the Massachusetts Eye and Ear Infirmary, Harvard Medical School and Harvard School of Public Health, conducted the largest study of twins of its kind. Analyses of monozygotic (identical) and dizygotic (fraternal) twins showed that genetic factors play a substantial role in the etiology of AMD and associated macular characteristics, explaining 46 percent to 71 percent of the variation in the overall severity of the disease. They found that environmental factors unique to each twin also contribute to the occurrence of this disease. This quantification of relative contributions to the development of AMD should guild further research on this important cause of blindness. Their findings were published in the March issue of Archives of Ophthalmology.
Johanna M. Seddon, M.D., ScM, director of the Epidemiology Unit at the Massachusetts Eye and Ear Infirmary and Associate Professor of Ophthalmology at Harvard Medical School, and her colleagues enrolled 840 twins throughout the United States who all had a complete ocular examination and photographs of the macula. Of these twins, 331 had no signs of maculopathy and 241 had early signs, while 162 had intermediate AMD and 106 had advanced AMD.
This is the largest twin study of AMD to date and the only population-based twin registry in the United States among elderly individuals. Authors quantified substantial genetic influences on AMD, contributed new information about the heritability of AMD, and established an important environmental contribution. “This twin study underscores the need for a multifactorial approach that incorporates genetic, environmental and biological factors to study the pathogenesis and clinical management of this blinding disease,” said Dr. Seddon.
Dr. Seddon and her colleagues have previously established that smoking and nutrition are modifiable factors associated with the development and progression of AMD. They are now also searching for the genes involved in the etiology of this increasing cause of blindness.
Adapted from the following source: Massachusetts Eye and Ear Infirmary