A cataract is a clouding of the lens in the eye, which usually occurs slowly over a number of years and gradually reduces vision until it is the equivalent of looking through frosted glass.
By far the most common cause of a cataract is advancing age. There is no specific cause for this, but people who live and work outdoors in very sunny climates seem to get the problem more. A small number of children have a genetic or inherited predisposition to develop a cataract early in life. Some babies are born with the problem. Patients with diabetes suffer the premature development of cataracts.
Uncommon causes of cataracts include ultraviolet, x-ray or gamma ray irradiation to the eye, exposure of a foetus to German measles (rubella) caught by the mother, damage to the eyes at birth due to lack of oxygen and a number of rare syndromes (e.g. lissencephaly syndrome).
The condition can be diagnosed by examining the eye with an ophthalmoscope (magnifying light).
Cataracts are initially treated with powerful spectacles, but eye surgery to replace the damaged lens is the best solution. Only one eye (usually the worst one) will be operated upon initially. Once this has recovered the second eye may be repaired.
A lens affected by a cataract can be surgically replaced with an artificial lens. The procedure can be done under a general or local anaesthetic and involves cutting open the top of the eye at the edge of the iris (the coloured part of the eye), removing the damaged lens by gentle suction, and inserting an artificial lens in its place. This new lens is not mobile and cannot change shape, thus spectacles are normally still required for close work, and sometimes distant vision as well.
The most noticeable effect after the operation is the brightness of the world. Colours in particular appear far brighter than the washed out appearance they have through a cloudy lens.
Complications may include dislocation of the new lens, or infection of the eye, but they are uncommon.
More than 95% of patients achieve excellent results with surgery.