Vitamin A - Essential for Healthy Eyes

The value of certain foods in maintaining health was recognized long before the first vitamins were identified. For example, liver has been used as a cure for ‘night blindness' for thousands of years. However, it was only in the early part of the 20^th century that researchers discovered that liver is a rich source of vitamin A, which is essential for healthy eyes.

Vitamin A is a pale yellow primary alcohol derived from carotene. Vitamin A was discovered by E.V. McCollum in 1913. The first vitamin A was called ‘fat soluble A', and in 1935 was found to be necessary for maintenance of normal vision.

The vitamin A we obtain from food comes in many different forms. These can be divided into two main types:

1. Provitamin A. The body obtains provitamin A by manufacturing it from carotene, a vitamin precursor found in vegetables such as broccoli, carrots, spinach, squash, and sweet potatoes.
   
   
2. Pre-formed vitamin A. The body absorbs ready-made vitamin A, often in the form of retinol, from plant-eating organisms. This animal form of vitamin A is found in liver, milk, butter, cheese, egg yolk, and fish-liver oil.

Vitamin A is involved in the production of a chemical known as visual purple. This chemical helps us see in dim light, when we enter a dark room from a brightly lit hallway.

Vitamin A is required by the photoreceptors of the retina for proper function. The visual system uses millions of photoreceptors to view, perceive, and analyze the visual world.

Vitamin A, as an antioxidant, has been shown to decrease lipid levels in coronary heart disease and therefore could be protective of the ocular vascular system (Singhal S et al 2001; Brown NA et al 1998).

Beta-carotene functions as an antioxidant by disabling free radicals. Low intake of beta-carotene is associated with increased free radical damage, which increases the risk of cataracts and macular degeneration (Mayne ST 1996).

One of the greatest nutritional breakthroughs in the treatment of macular degeneration was the release of the Age-Related Eye Disease Study, in which researchers found that vitamins C and E, beta-carotene, and zinc (plus copper) can reduce progression in certain types of macular degeneration (Age-Related Eye Disease Study Research Group 2001).

Vitamin A eye drops have been used to treat eye problems such as blurred vision, cataracts, glaucoma, conjunctivitis, and dry eyes.

Sufficient amounts of vitamin A can be obtained in a normally balanced diet. However, it is believed that one-third of American children consume far less than the recommended allowance of vitamin A.

Since vitamin A is fat-soluble, a deficiency rarely occurs. However, one of the first symptoms, should you become vitamin A deficient, would be night blindness (difficulty adjusting to darkness) due to lack of visual purple. Another version of night blindness, also known as glare-blindness, is the inability to regain focus of the road after the glare of passing car headlights.

Prolonged vitamin A deficiency leads to exophthalmia, which is a condition in which eyes become dry, ulcers appear on the cornea, the eyelids become swollen and sticky, and eventually leads to blindness. Vitamin A deficiency is the leading preventable cause of blindness in developing countries.

Maintaining normal vision is just one benefit that vitamin A provides. Even though vitamin A was the first vitamin discovered, we have yet to uncover all there is to know about this amazing nutrient and its healing capabilities.