Age-related macular degeneration, a major cause of vision loss and blindness among the elderly could be the result of two gene mutations.

While not a cure for AMD, scientists believe the discovery could bring doctors closer to therapies that could help prevent or treat the disease. Macular degeneration causes the deterioration of the macula, a part of the retina.

A research team from Columbia University in New York City found specific variations in the two genes that may account for about three-quarters of all cases of age-related macular degeneration. The study suggests that the immune system plays a crucial role in the development of macular degeneration, because the presence of the gene variations alone doesn’t mean a person will develop AMD. A trigger must be present, as well.

An estimated one-third of Americans will develop some form of macular degeneration by the time they are age 75. The research was reported online in Nature Genetics.