Gene linked to major eye illness

Age-related macular degeneration, the leading cause of blindness among Canadians over the age of 50, is linked to a genetic mutation, researchers have found.

The condition affects about 15 million people in North America. Their vision is blurred in the macula, the part of the eye that perceives details in central vision.

The genetic discovery raises hopes of earlier detection of the disease. It likely won't lead to more treatment options for about 10 years, the researchers cautioned.

Robert Klein of Rockefeller University in New York and his colleagues searched through thousands of variations in gene sequences before they found one linked to the eye condition.

A variation in the gene CFH on chromosome 1 is tied to the age-related macular degeneration, Klein's team reported in this week's online issue of the journal Science.

The investigators estimate the mutation could increase the risk of developing the condition by three to seven times.

Two other research teams based at the University of Texas at Dallas and Vanderbilt University Medical Center in Nashville, Tenn., independently confirmed the gene discovery.

The gene was identified by comparing DNA of patients with AMD to those without it.

The studies suggest the CFH gene is involved in producing a protein that regulates inflammation of the immune system.

• FROM JAN. 13, 2005: Eye disease drug awaits approval in Canada

"This gene opens the door to a whole new understanding of the factors that contribute to this disease," said one of the study's authors, Margaret Pericak-Vance, director of the Duke Center for Human Genetics.

"The finding may ultimately lead to new methods for identifying those at high risk for macular degeneration and suggests new pathways for drug development," she added in a release.

Caucasian people with AMD are four times as likely to have the CFH mutation as people without the disease, said Klein collaborator Josephine Hoh of Yale.

But the mutation is not the only cause of macular degeneration, which contributes to inflammation. Family history is a major factor, and environmental conditions also play a role.

Smoking, obesity and a diet high in fat raise the risk of AMD; eating fruits and vegetables lowers the risk.