Classification and causes of cataract
Cataracts may be classified based on several factors, including the age of the person when the cataract was first detected, the cause of the cataract and whether it is an inborn (genetic) or acquired problem. Some of the causes include physical injury to the eye, long-term exposure to very bright sunlight, or to the fumes and smoke from household cooking fires, cigarette smoking, poor control of diabetes mellitus (the high sugar levels in the blood damages the eye), and so on. All of these factors reduce the clarity of the lens over time. The susceptibility to develop cataracts can also be transmitted in the genes from parent to child.
You should also know that deficiency of vitamin A from the food we eat is an important cause of blindness. To prevent blindness from vitamin A deficiency, infants are given a supplement of vitamin A drops with measles vaccine, repeated every six months until the age of five years.