Age-related macular degeneration (AMD) causes loss of vision for more than 7 million people in the United States each year–the bulk of them senior citizens. It happens when a layer of tissue between the retina and the blood vessels behind the retina breaks down, causing proteins and lipids (fat cells) to build up in the center of the eye. No one is quite sure what causes AMD, though some studies have shown that genes play a part in some cases of early onset macular degeneration. One of the most likely genetic causes is from a group of genes that regulate a type of protein called fibulin. Scientists from the Center for Macular Degeneration at the University of Iowa looked at the genetic makeup of people with AMD to see if the genes regulating their fibulin production were normal.

What the researchers wanted to know: Are there mutations in the genes that code for the protein fibulin that are common in people with AMD?

What they did: The researchers analyzed the genetic makeup of 402 patients with AMD and compared them with the genes of a few hundred people without AMD. Most of the people screened for this study were patients at the Retina Clinic at the University of Iowa . The researchers compared the genes of people with AMD and those without, and looked at whether abnormalities could cause the body to alter the way it produced fibulin proteins.

What they found: In all, the researchers found 27 variations in the fibulin genes in the patients with AMD that were not seen in those without the disease. However, only variations in one fibulin gene, called fibulin 5, were seen in significantly more AMD patients. Seven AMD patients had a mutation in fibulin 5, while none of the control subjects did.

What it means to you: While the variation in fibulin 5 was found in less than 2 percent of AMD patients, it's still a link between this class of genes and AMD. As the scientists point out, because AMD does not develop until later in life, the genetic abnormalities associated with it are likely to be quite subtle. There is still a long way to go before AMD can be cured, but this study at least points scientists in a promising direction for further research.

Caveats: For most of the AMD patients, the scientists did not find any genetic mutations in the fibulin family, suggesting that this group of genes may only be one of many, many more that should be looked at.

Find out more: The National Institutes of Health Medline has a good description of AMD

Read the article: Stone, E.M. et al. "Missense Variations in the Fibulin 5 Gene and Age-Related Macular Degeneration." New England Journal of Medicine. July 22, 2004, Vol. 351, No. 4, pp. 346-353.

Abstract online: http://content.nejm.org