There are about 12 million people who are blind in the United States. They are male and female, of all ages. What they all have in common is that their vision cannot be corrected and their vision makes it more difficult to do major life activities such as driving, etc. This can also be called visual impairment.
Legal blindness is defined in several ways. One is that a person has vision of 20/200 or less. This means that this person sees at 20 feet that a normally sighted person would see at 200 feet. Many people have this condition and it can be fixed with glasses. A person who is blind in this way has vision that cannot be corrected with glasses or contact lenses.
Another way a person can be blind is to not have a total “visual field”. This means that a person cannot see the whole scene as a normally sighted person can. This is measured in degrees. A person with a visual field of less than 20 degrees is considered legally blind. Normally sighted people have a visual field of 180 degrees in a normal eye.
In the picture below you see the normal visual field with the line that goes across. The circle in the middle indicates the visual field for someone who is legally blind which is much smaller than that of the normal visual field for someone who would see more of the fish.
Some people are what is called color blind. This means that they do not see colors as most people see them. Although they are called color blind, they are not really legally blind and they can usually drive, and do things more easily than someone who is legally blind.
Most people who are blind have a little sight of some sort or can sense light. However, their vision may make it difficult to recognize people by sight, read easily, or need different lighting. Many of them have what is considered low vision and use magnifiers, special lamps and other visual aids to allow them to use the sight they have.