The aging lens suffers metabolic changes that may predispose it to cataract development. Some of this occurs due to low supply of oxygen and nutrients, which leaves the eye open for free-radical damage. According to Garner et al. (1983), cataracts are initiated by free-radical hydrogen peroxide found in the aqueous humor. Free radicals, such as hydrogen peroxide, oxidize glutathione and destroy the energy-producing system of the eye and allow leakage of sodium into the lens. Water follows the sodium, and the edema phase of the cataract begins. Then, body heat in the lens of the eye oxidizes (cooks) lens protein, and it becomes opaque and insoluble (similar to egg protein).
Free radicals reside in the aqueous fluid and bathe the lens of the eye, destroying enzymes that produce energy and maintain cellular metabolism. Free radicals also break down fatty molecules in membranes and lens fibers, generating more free radicals and creating a cross-linking (denaturing or breakdown) of the laminated-like structural proteins inside the lens capsule. The lens capsule has the ability to swell or dehydrate. In doing so, the increase and/or decrease in pressure can cause breaks in the lens fiber membranes, resulting in microscopic spaces in the eye in which water and debris can reside (KaLuzny et al. 1997).
Although it is difficult to treat cataracts with oral antioxidants since there is only minimal blood circulation within the eye compared to other parts of the body, nutritional supplements have been shown to reduce the risks of cataracts as well as slow or reverse their progression (Bantseev 1997).
The eye consists of 65% water and 35% protein (the highest protein content in the body). The eye also contains the highest percentage of potassium in the body, along with a high percentage of vitamin C and glutathione.
Higher levels of glutathione are present in the cortex (edge) of the lens, preventing free radical-induced photochemical generation of harmful by-products. Oxyradicals (free-radicals) generate cataracts, and experiments demonstrate that glutathione reactivates oxidized vitamin C, which in turn improves antioxidant potential within the lens. Vitamin C, selenium, and N-acetylcysteine (NAC) fight free-radical damage and help increase vital levels of glutathione.
It is crucial for cataract patients to wear protective eyeglasses to shield against free-radical damage induced by UV sunlight. If UV-blocking sunglasses were to be worn throughout life, the risk of cataract would be reduced greatly. Exposure to sunlight is a major risk factor in the development and progression of cataract disease. Low-cost, wrap-around sunglasses are available; they fit over regular glasses to provide almost 100% protection against UV penetration to the eye.