Carotenoids are plant pigments that have antioxidant activity. The dominant carotenoids in the whole retina are lutein and zeaxanthin. Zeaxanthin is concentrated in the macular region, whereas lutein is dispersed throughout the entire retina, according to Investigative Ophthalmology & Visual Science (1988 Jun;29(6):850-5). A recent article appearing in Nutrition Journal (2003, Dec. 11, 2:20) speculates that the intake of these carotenoids may help prevent macular degeneration. Low levels of these carotenoids seem to be related to a higher risk of macular degeneration. Studies are inconclusive. The Medical Journal of Australia (2006; 184 (9): 455-458) cites a large study that investigated the use of antioxidants (high doses of vitamin C, 500 mg; vitamin E, 400 IU; β-carotene, 15 mg) and zinc, 80 mg, with progression of AMD.33 They followed up 3640 participants for an average of 6.3 years. They showed that the use of antioxidants and/or zinc in the 2577 participants with a high-risk of age related macular degeneration (AMD) resulted in a reduced risk of disease progression. The results were not as conclusive in the lower-risk group.

Carotenoids may improve vision in general, even in healthy subjects. Researchers gave 40 subjects 12 mg of lutein and zeaxanthin daily for a period of six months in study that appeared in Optometry and Vision Science (2008 Feb; 85(2):82-8). The subjects had improved visual performance under high-glare conditions. The researchers believed that the carotenoids increased the macular pigment optical density, thus improving vision. This supports other research that showed supplementation with lutein and zeaxanthin improved vision under low-light conditions (Opthalmic and Physiological Optics; 2006 Jul;26(4):362-71)