More than any other tissue in the body, the ocular lens and retina are continually exposed to oxygen and intense light radiation. Both light and oxygen can create free radicals that play havoc with membrane lipids of visual cells. Experts believe that the uncontrolled generation of free radicals in the eyes can ultimately lead to macular degeneration and cataracts. Therefore, ocular tissue relies on a strong antioxidant defense system to protect them from free radical damage. Extracts of bilberry and Ginkgo biloba, green tea, rutin, quercetin, and hesperidin are a rich source of flavonoids that provide potent antioxidant defense in retinal visual cells and help maintain healthy vascularization in ocular tissue. Glutathione and selenium are essential components for healthy activity of the antioxidant enzyme glutathione peroxidase which is abundant in healthy eyes. Glutathione peroxidase levels, however, decline with advancing age, and an adequate dietary supply of glutathione, its precursor N-acetyl-L-cysteine, and selenium may help maintain healthy levels of this important enzyme. Beta-carotene serves at least two purposes for the eyes. It is a valuable precursor for vitamin A which functions in the retinal cells as a light receptor. Beta- carotene, as well as other carotenoids in Macushield, such as lutein and lycopene, are also important antioxidants in the lens and retina. Zinc is not only essential for normal visual signal transduction in the retina, but also is part of many of the enzymes involved in vitamin A dependent light reactions in retinal cells. Moreover, zinc, as well as copper and manganese, are essential cofactors of superoxide dismutase, an antioxidant enzyme that removes potentially dangerous superoxide radicals in the visual cells, the lens, and other tissues. Taurine, the most abundant free amino acid in ocular tissue, is thought to help stabilize neural membranes in retinal cells and modulate photoreceptor activity.