When the amount of free radicals in the body exceeds the capacity of the scavengers, aging and injurious processes begin. This degeneration is called oxidative stress . Although deficiencies in these substances have been noted in patients with AMD, evidence of the ability of these supplements to protect the retina and thereby prevent or slow the progress of the condition is not yet certain. The substances you are most likely to hear touted as protection from AMD are lutein and zeaxanthin. Lutein, a xanthophyll, is found in marigold flowers, spinach, kale, collard and mustard greens, egg yolks, and certain hormones.
Plants produce many types of xanthophylls, but lutein is the only one that accumulates in the eye.
Closely related to lutein, zeaxanthin seems to produce thicker, more protective macular pigment. In a recent 15-week study, people given a diet high in fruits and vegetables which are rich in lutein and zeaxanthin demonstrated increased plasma levels of these nutrients and increased density of their macular pigments. The control group, given a diet low in these carotenoids, did not show these increases. A powerful antioxidant, lutein accumulates in the very center of the retina, forming the macula lutea. It helps filter out the blue spectrum of sunlight, which can increase drusen.