Studies have shown that antioxidants play a role in certain important eye conditions like Age RelatedMacular Degeneration [ARMD], cataract and diabetic retinopathy.
Causes of eye damage
Cataract:
Clouding of the transparent lens of the eye is called a cataract. Oxidative stress, which causes damage to the lens proteins is proposed to be a cause of cataract and hence an appropriate antioxidant could halt the process and delay vision impairment caused by cataract.
Age Related Macular Degeneration [ARMD]:
It is one of the leading causes of irreversible vision loss in many countries across the globe. As longevity increases in developing nations, ARMD is emerging as a public and personal health issue that markedly compromises the quality of life among the affected elderly.
Normal metabolic processes and UV light absorption generates free radicals and oxidants causing damage to the retinal photoreceptors. This leads to impaired function and eventually to degeneration of the macula. The macula is a central part of the retina responsible for central vision [reading, driving, handwork] and is directlybehind the lens. The macula is the area of the eye that receives the most light. These radicals and oxidants are eliminated by antioxidants, which helpin preventing cellular damage in the retina.
Diabetic retinopathy:
The effect of diabetes on the retina of the eye constitutes diabetic retinopathy, which may cause mild to moderate damage to the retina in the form of blood leaks to a severe form which can lead to blindness. The extent of oxidative stress [an imbalance in the levels of oxidants and antioxidants] is related tothe severity and duration of diabetes.
The level of antioxidants is significantly decreased in diabetes. This suggests that antioxidants can play a vital role in prevention and progression of diabetic retinopathy. Vitamin E and C are important components of cell defence against oxidative stress and more so in diabetic retinopathy.
Sources of antioxidants
There are a number of antioxidants that pack a lot of power for the eyes. These include vitamin A and carotenoids, vitamin C, vitamin E, anthocyanidins, selenium and zinc, which are found naturally in food.
Vitamin A is a super oxidant known primarily for its effect on the retina and also for improving night vision. It is found in eggs, fish, fish liver oil and liver. 
Vitamin C is found in orange, grapes, papaya, tomato, and strawberries.
Vitamin E can be obtained from almonds, sunflower seeds, safflower oil, peanuts and peanut butter.
Anthocyanidins is found in blueberries and bilberries.
Carotenoids, nutrients that are not classified as vitamins, include beta-carotene, alpha-carotene, lycopenes, lutein and zeaxanthin.
Lutein is an antioxidant that has been shown to be associated with a reduced risk of macular degeneration and cataract. As an antioxidant, it is 10 times more effective than vitamin E.
Lutein and zeaxanthin are deposited specifically in the macula and their function is to reduce oxidation. They filter out blue light that is known to cause free radical damage to the eyes.
It is estimated that foods or supplements high in lutein and zeaxanthin eaten five times per week could significantly reduce ARMD. Because both lutein and zeaxanthin are fat soluble, they should be taken with meals or olive oil.
Super foods that contain carotenoids include broccoli, brussels sprouts, leaf lettuce, spinach, collard greens, sweet potatoes, carrots, mangoes, papaya, egg yolk, milk, apricots and tomatoes.
Many different brands of antioxidant supplements are sold singly and in various combinations as tablets, capsules and sprays. The manufactured quality and formulation of the supplement can influence absorption and therefore potential benefit.
It is important to remember that vitamin supplements are not a cure for ARMD or other eye conditions, nor will they restore vision already lost from the disease. However, specific amounts of these supplements do play a key role in helping some people at high risk to maintain their vision. But the best way to good eye health is to have a healthy diet with fresh fruits and vegetables.
An important study
The Age Related Eye Disease Study [AREDS] of the National Eye Institute, USA is the most powerful ophthalmologic clinical trial till date, which was designed to investigate the role of high dose vitamin C, vitamin E, beta-carotene and zinc on both Age Related Macular Degeneration [ARMD] and cataract. The results showed that acombination of zinc and antioxidants offers modest benefit with respect to prevention and further progression of ARMD.
There are no statistically significant serious adverse effects associated with antioxidant treatment. Incidences of genitourinary disorders are more frequently seen in thosereceiving zinc. Zinc supplements may also depress copper levels leading to copper deficiency anaemia and hence copper should be taken with a high dose of zinc. Antioxidants like beta-carotene should be avoided in groups of people at high risk for cancer [smokers].