What is the Legal Definition of Blindness?
Legal blindness occurs when a person has central visual acuity (vision that allows a person to see straight ahead of them) of 20/200 or less in his or her better eye with correction. With 20/200 visual acuity, a person can see at 20 feet, what a person with 20/20 vision sees at 200 feet.
In determining legal blindness, visual field (the part of a person's vision that enables them to see what is happening to the side of them) is also considered. A visual field of 20 degrees or less is considered to be legally blind. Eye care professionals can assist in diagnosing legal blindness.
What is "Functional" Blindness?
The Iowa Department for the Blind also serves individuals who are functionally blind. A person is functionally blind when they have to use so many alternative techniques to perform tasks that are ordinarily performed with sight that their pattern of daily living is substantially altered. Such alternative techniques might include reading a newspaper by listening to it over the telephone or using Braille to read a book.
What is Low Vision?
A person who is low vision has difficulty performing ordinary tasks with sight – even with the best glasses or contact lenses.
Simulations of Vision Loss
About 80 percent of individuals who are blind have some remaining vision. It may be difficult to understand how an individual with a certain eye condition can see some things while not seeing others. While some people lose a lot of vision in a short period of time, others lose vision slowly. Many diseases that cause blindness begin to affect a certain part of vision and then progress to take away more vision. For example, macular degeneration initially affects a person's central vision (