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What is a cataract?

To see clearly, the eye has to adjust its focus continually for objects that are at different distances from the eye. This function is performed by the lensThe lens fulfils the same role as the lens in a camera. It handles about one-third of the focusing power of the eye and is critical for good vision.See Info on Eyes – Anatomy. of the eye, which is located just behind the pupil and iris (the coloured part of the eye). The lens has to be clear and transparent for good vision. If, for any reason, the lens starts becoming cloudy and opaque, it is termed a 'cataractA cataract forms when the natural lens in the eye is, or is starting to become, opaque. If not treated, it can lead to blindness, which in most cases can be treated. See Cataract Centre – Understanding Cataracts.'.  Therefore, a cataract is really a lens that is already, or starting to become, opaque.

What causes a cataract?

A cataract may be caused by many different factors, but the common cataract occurs with increasing age. These cataracts develop slowly over a matter of months or years and the only noticeable symptom is a steady decrease in vision. General illumination and brightness decreases and occasionally an object may appear as a double image when looking at it with one eye. Some patients will experience a decrease in vision in bright sunlight, while others find their vision to be worse at night.

Other causes of cataracts occur in newborn infants, often as a result of the mother having had German measles during the first 3 months of pregnancy. Injuries are also common causes of cataracts and may develop overnight as result of a direct blow to the eye or the piercing of a sharp object or foreign body into the eye. Diabetic patients seem to develop old age cataracts more often.

Clearly the common old age cataract develops as a result of the decline in the normal maintenance of the health and nutrition of the lens. Unfortunately, no drops or medication can halt this process. Moreover, some patients have a hereditary tendency to develop cataracts.