This article does not have any sources. (September 2010)
In modern countries, few young people are blind. In all the world, blindness is mostly caused by malnutrition and diseases of old people, like cataracts and trachoma. People can become blind because of diseases or accidents, but sometimes people are born blind.
Legal blindness is defined as a level of visual acuity low enough to qualify for disability benefits and\or special accommodations. Legal blindness is also defined as being unable to be completely corrected by prescription glasses or contact lenses.
Some people are color blind, which means they can see, but cannot tell certain colors apart.