Fish oil supplements may boost your immune system, but they may not be as helpful for age-related vision problems.

That’s the finding of a large study conducted by the National Eye Institute (NEI). Fish oil supplements that contain omega-3 fatty acids do not appear to prevent age-related macular degeneration, a leading cause of blindess in those 50 and up, according to NEI.

“Millions of older Americans take nutritional supplements to protect their sight without clear guidance regarding benefit and risk,” said NEI director Paul A. Sieving in a press release. “This study clarifies the role of supplements in helping prevent advanced AMD, an incurable, common, and devastating disease that robs older people of their sight and independence.”

NEI conducted a a study of 4,200 people between the ages of 50 and 85 who were at risk for advanced age-related macular degeneration. A 2001 study had determined that “daily high doses of vitamins C and E, betacarotene, and the minerals zinc and copper … can help slow the progression to advanced AMD,” according to the NEI press release.

The recent study, known as Age-Related Eye Disease Study 2 (AREDS2), tested to see if the original study’s formulation could be improved by “adding omega-3 fatty acids; adding (antioxidants) lutein and zeaxanthin; removing beta-carotene; or reducing zinc.” Over the course of five years, study participates took one of four different formulations every day. Researchers found that while fish oil supplements, lutein and zeaxanthin didn’t appear to affect AMD when added to the combination, the latter two were a lot safer than betacarotene, which has been linked to lung cancer in smokers.

In fact, lutein and zeaxanthin without betacarotene led to an 18 percent decrease in the chance of AMD for participants. Those who had low amounts of lutein and zeaxanthin in their diet who took it during the course of the study had a 25 percent decrease in the chance of AMD. The two antioxidants can be converted into vitamin A which, when found in the retina, can decrease the amount of UV damage in the eyes.