Why are some people blind?

Blindness is complete loss of sight. It can happen when the optic nerves, which carry visual signals from the eyes to the brain, or the sight centers of the brain are damaged. Such damage can occur as a result of injuries or diseases. A person can also be born with eye or brain abnormalities that cause blindness. In many cases, particularly in very poor countries, infectious diseases and poor diets can also cause blindness. A lack of vitamin A, in fact, is the leading cause of blindness worldwide. With basic medicines and proper nutrition, such cases could be prevented. For every one person in the United States who is totally blind, there are four others who are visually impaired or “legally blind.” These people have some ability to see, but they see so poorly—even with eyeglasses—that they cannot do things that require good vision, like driving a car.