Cataracts cause progressive, painless loss of vision. The lens clouds naturally as we age, so people over the age of 65 usually see a gradual reduction of vision. No one is exactly sure what causes cataracts.
In younger people, they can result from an injury, certain medications or illnesses such as diabetes. Prolonged exposure to ultraviolet light may also play a role in the formation of cataracts. Studies have also shown that cigarette smokers have a higher risk of developing cataracts than non-smokers.