General EYE ADVICE

Cataract - Causes and Prevention

 The eye normally has a clear lens in it, which is suspended in the fluid of the eye by means of fibers around the lens that are attached to a muscle inside the eye. This muscle is attached to ligaments and when it contracts the lens power changes, thus enabling the focusing action of the eye. Many factors can disturb the structure of the molecules in the lens material, leading to cataract formation. In this condition the light that passes through the lens is scattered by the opacities thereby affecting the clarity of the vision. The effect on the vision is similar to that obtained when looking through a scratched or fogged glass.

Probably the most important factor in cataract formation is UV radiation from sunlight. UV and visible blue light carry relatively high energies and can affect the state of the atoms in the lens tissue. This can potentially trigger a series of chemical (oxidation) reactions that can disturb the normal molecular structures of the lens material, leading to opacities. To stop this damaging chain of reactions, chemical compounds of a particular type are required, called anti-oxidants. These compounds can effectively stop the chain of oxidative reactions in a process called reduction.

A nutritious, well-balanced diet, which is adequate in fruits, grains and vegetables, is needed for an adequate supply of anti-oxidants. Vitamin E and C and the carotenoids like beta-carotene, are examples of anti-oxidant vitamins. Vitamin E can be found in nuts and vegetable oils, vitamin C can be found in fruits, especially citrus fruits, and beta-carotene which is required to make vitamin A, is found in many plants e.g. carrots. Apart from the vitamin form, anti-oxidants are also present in the enzyme form. These enzymes require certain minerals for proper activity e.g. zinc, copper and manganese.

From this information, it follows that if we wish to prevent cataracts, we must consider at least two preventive measures. First, we need to decrease the amount of UV and visible blue light to which the eyes are exposed. Simple and obvious, yet very effective techniques to accomplish this, include minimising the time spent in bright sunlight and using a hat and/or sunglasses to protect the eyes. Second, the body's protective mechanism should be maintained at optimum levels by ensuring an adequate supply of the anti-oxidant vitamins and minerals. These nutrients are best obtained by simply eating a balanced diet, high in fruits, grains and vegetables. Examples are wholegrain bread and pasta, corn, oats and spinach.

Some people may need to use vitamin supplements for various reasons. Their life-style or other circumstances may not allow for healthy eating, they may have problems in digesting food or absorbing nutrients from the gut, or may require very high levels of anti-oxidants because of smoking or unavoidable high exposure to UV radiation. Smoking can markedly increase the oxidative chemical activity and can use up much of the body's supply of anti-oxidants. "Eyevite" is one of a few brands of vitamin tablets that were developed to cater for eye's vitamin needs. (The above information and the information below on AMD was partly sourced from a lecture given by Diane P. Yolton of Pacific Uni. College of Optom. at the eleventh APOC held in Korea in 1997.)   

Adequate UV protection can be obtained from sunglasses that meet the necessary standards for UV protection. For those people who require to wear a correction, UV protection can be obtained in various ways. The lenses can be dyed with a clear UV filter alone if glare protection from visible light is not required. A clip-on may then be used whenever glare protection is required. Alternatively, prescription lenses which are dyed with a UV filter can be tinted to whatever colour or density is required and can be used as sunglasses. Prescription lenses that darken in sunlight may be used either for reasons of cost or convenience.

There are several other causes of cataract apart from UV radiation and poor diet. Examples are: poor general health due to diabetes or asthma, smoking, some types of medication (especially oral cortico- steroids) and eye disease such as glaucoma and internal eye inflammation (uveitis).

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