There are many kinds of visual problems. People who are blind have little or no useful vision. Legally, blindness can be defined in two ways:
- A person’s central visual acuity is 20/20 or less in the better eye with the best possible correction. In other words, a person can recognize objetcs at a distance of 20 feet that a person with normal vision can recognize at 200 feet.
- A person’s peripheral vision is severely restricted to an angle no greater than 20 degrees. In other words, a blind person with this problem can only see a very limited area at one time. He/she cannot make much practical use of his/her vision.
Partially sighted people have visual acuity between 2-/200 and 20/70 in the better eye. Many people with visual impairments have some remaining vision. These are typical terms:
- Myopia – nearsightedness
- Hyperopia – farsightedness
- Astigmatism – a condition in which a person sees distorted images.
- Cataracts – a condition in which there is clouding of the lens of the eye causing blurred vision
- Glaucoma – a build-up of fluid behind the eye
Only one in 1000 people are legally blind.