Medical therapy in the prevention of cataract.

Medical treatment of cataract depends on understanding the mechanism of cataract formation. This is established in sugar cataract, in which sugar is metabolised to sugar alcohol. Sugar alcohol accumulates and the resultant osmotic stress is considered to cause lens fibre damage. The conversion of sugar to alcohol is effected by the enzyme aldose reductase and interest now centres around the use of aldose reductase inhibitors. A controlled clinical trial into the effect of the spirohydantoin Sorbinil in adult diabetic cataract has started at Oxford. Aldose reductase inhibitors may also act on non-diabetic cataract, which is supported by some clinical evidence. The biochemical basis of this and other possible treatments for cataract are outlined.