First we need to understand what free radicals are. They are atoms that are lacking a particle called an electron. This makes them very unstable. In their attempt to become stable, they attack other cells and try to "steal" an electron. This attack harms the cells delicate membranes, thereby making them a target for disease.

This process is called oxidation. Just like oxygen causes metal to rust, oxidation can also damage cells. In humans, the common signs of oxidative damage can be seen in the normal signs of aging, such as skin changes, including wrinkles, and ocular changes, like cataracts and macular degeneration.

Anti-oxidants neutralize free radicals by donating an electron to the unstable cells. After being neutralized, those free radicals will no longer attempt to damage cells, and therefore become less harmful to the body.

The body makes some of its own anti-oxidants including glutathione, super oxide dismutase, and coenzyme Q10. Nutrients such as selenium, riboflavin, zinc and cysteine are needed to help the body produce these anti-oxidants.

Ultraviolet sunrays promote oxidation. If you stare at the midday sun, the UV rays can "oxidize" retinal cells at the back of the eyes, resulting in a short time in a loss of central vision. Similarly, the destruction of retinal cells can occur slowly over many years, from low levels of sunlight and/or from a gradual reduction in the anti-oxidant defense system.

The reduced level of anti-oxidants in the eyes as we get older is believed to be a major factor in the decrease of sight.