From the National Eye Institute:
Researchers with the Age-Related Eye Disease Study (AREDS) reported in 2001 that a nutritional supplement called the AREDS formulation can reduce the risk of developing advanced age-related macular degeneration (AMD). The original AREDS formulation contains vitamin C, vitamin E, beta-carotene, zinc and copper.
In 2006, the same research group, which is based at NIH's National Eye Institute, began a second study called AREDS2 to determine if they could improve the AREDS formulation. They tried adding omega-3 fatty acids, as well as the antioxidants lutein and zeaxanthin, which are in the same family of nutrients as beta-carotene. The researchers also tried substituting lutein and zeaxanthin for beta-carotene, which prior studies had associated with an increased risk of lung cancer in smokers. The study found that while omega-3 fatty acids had no effect on the formulation, lutein and zeaxanthin together appeared to be a safe and effective alternative to beta-carotene.