Most cataracts develop slowly over time and affect people over age 50. About half of the U.S. population has a cataract by age 65, and nearly everyone over age 75 has at least a mild cataract in one or both eyes.
In rare cases, infants can have congenital cataracts. These usually are related to the mother having German measles, chickenpox, or another infectious disease during pregnancy; but sometimes they are inherited.