Macular degeneration involves the deterioration of the macula, located in the back of the retina and responsible for the acuity of a person's central vision, and occurs mostly in aging men and women.
It affects more than seven million people in the United States over 40 years old, and with no clear way to prevent its onset.
But scientists in the Age-Related Eye Disease Study Research Group, supported by the national Institutes of Health, found people who consume more omega-3 fatty acids -- found in large amounts in fish like tuna and salmon -- have a lower incidence of advanced age-related macular degeneration (AMD), according to a summary of the study.
They also found that those who show higher blood levels of vitamin D appear to have a lower chance of the early stages of AMD.
"Milk intake was inversely associated with early AMD. Fish intake was inversely associated with advanced AMD," they said.
The research group studied 4,519 people who were between 60 and 80 when the study began in the 1990s. Of them, 1,115 had no AMD symptoms at the beginning, while 658 had severe AMD.
The researchers found that those in the first group had high levels of omega-3 fatty acid consumption while those with severe AMD had corresponding low levels.
"Eating more than two medium (4-ounce, 110 grams) servings of fish per week or more than one medium serving of broiled or baked fish was associated with the lowest risk for advanced AMD," the researchers said.
They postulated that the fatty acids may protect the retina by promoting cell survival and the functioning of blood vessels, as well as affecting specific gene activation.
The vitamin D study results meanwhile suggested that vitamin D might reduce inflammation of the retina, or prevent the growth of new blood vessels, which contributes to some types of AMD, the scientists said.
The two studies are published in the May issue of Archives of Opthamology