Vision vitamins are an important component of our everyday diet. Apart from the vitamin A which is widely known for its important properties, there are many others that play a central role in maintaining good eyesight. These nutritional elements include vitamin B6 and C and others such as selenium, zinc and magnesium among others. There are many different types of foods that contain many of these elements in different combinations. Examples include green leafy vegetables, oranges, carrots and pumpkins among others.

We will explore the benefits of vitamin A in more detail since it is the nutrient of greatest significance. The vitamin is involved in the synthesis of a pigment of the retina known as rhodopsin. Rhodopsin is necessary for dim vision. The other important role that this pigment plays is that it helps to keep the cornea moist through the maintenance of the integrity of related membranes.

The A vitamin is not a single unit as such but is composed of a group of hydrocarbons which are not saturated. These include retinoic acid, retinal, retinol and a number of vitamin A precursors (carotenoids). The most important among the pro vitamin A carotenoids is beta carotene. Retinal component combines with the protein opsin to form rhodopsin. The so formed light absorbing molecule is vital for both colour and low light (scotopic) vision.

Lack of vitamin A causes many eye problems whose severity varies depending on the period of time one is affected and the extent of deficiency. Such a deficiency will be caused by inadequate amounts of vitamin A in the diet for a long time. This is called primary vitamin A deficiency. Its prevention entails frequent intake of carotenoid containing foods such as fruits, vegetables and dairy products.

The secondary form of deficiency is as a result of malabsorption of lipids and deficient bile production and release. This is explained by the fact that the A vitamin is a fat soluble vitamin and therefore requires dissolution in fat in fat for it become functional in the body. As such, a low fat diet can predispose one to disease states related to deficiency of respective vitamins. Long term exposure to oxidants including cigarette smoke and alcohol intake can also lead to secondary insufficiency of vitamin A.

Night blindness is one of the commonest and earliest symptoms of deficiency. One of the causes of reduced vision is drying of the conjunctiva which takes place as the condition progresses. The normal secretory system is progressively replaced with hardened keratinised tissue. As keratin plaques are eroded progressively, more keratinisation takes place.

The other vitamins play a relatively minor role. Vitamin C has antioxidant properties which help protect the eye from irradiation. It is also important in the maintenance of capillary integrity and normal pressure. The B6 vitamin maintains red cell structure and function and thus ensures that the retina functions optimally. Zinc takes part in the conversion of beta carotene to vitamin A.

While it may not be possible to have all these vision vitamins in the diet at all times, it is wise to have them as many times as possible. The factors that determine intake include, among others, pregnancy, lactation, sex and age. It is important to take just enough in each serving to avoid toxicity.