The hypothesis that beta-carotene levels are inversely related to AMD is supported by experimental studies on the relationship between antioxidants and retinal morphology and function. There is increasing evidence that visible and ultraviolet light can damage the retina through production of superoxide radicals. Antioxidants (including beta-carotene, vitamins A, E, and C, and selenium) protect against oxidative damage by acting as scavengers for the superoxide radicals.