Eating foods rich in omega-3 fatty acids, such as salmon and tuna, seems to be good for not only the heart and mind but the eyes. A new study adds shellfish to that group. It found that seniors who ate at least one serving a week of fish or shellfish high in omega-3s reduced their risk of developing advanced age-related macular degeneration, a disease that affects vision, by 60 percent.

The findings are consistent with mounting evidence that high levels of dietary omega-3 fatty acids benefit eye health, the researchers said.

"But, unlike previous studies, we included shellfish intake in the determination of omega-3 fatty acid consumption," said researcher Bonnielin K. Swenor of the Wilmer Eye Institute at John Hopkins University. "This is important because shellfish, particularly crab and oysters, are a main component of the diet" of the study population.

Age-related macular degeneration (AMD ) is a chronic and irreversible condition that kills the cells in the macula, the part of the eye responsible for seeing fine detail. Some 1.8 million Americans age 40 and older are affected by AMD, according to the Centers for Disease Control and Prevention. It is a leading cause of vision loss for people 60 and older, according to the National Eye Institute.

The researchers asked 2,391 people, ages 65 to 84 , in eastern Maryland how much fish and shellfish they ate. Of the people in the study, 1,943 did not have any form of AMD, 227 had the disease in the early stage, 153 had intermediate-stage AMD, and 68 had advanced-stage AMD.

The researchers found that those who ate at least one serving a week were 60 percent less likely to have advanced AMD than those who ate less. At the same time, however, the researchers said they didn't find that high intake of omega-3s protected against two early markers that often precede the development of AMD.

They also assessed intake of crab and oysters foods high in zinc. Unlike other studies that have suggested zinc stalls the progression of certain types of AMD, Swenor and her colleagues found no protective effect.

More studies should be done, Swenor said, to fully understand the mechanisms behind the effects of omega-3s and zinc on the risk of AMD.

Swenor and her team plan to continue to examine the link between diet and the risk of AMD.

Their study will be published in the December issue of the journal Ophthalmology.