Normal vision, or 20/20, means a person sees the smallest letters or pictures on an eye chart when standing 20 feet away from the chart. Some people cannot see normally, even with glasses or contacts, because a medical condition affects their vision. These people are called visually impaired or visually handicapped.
If a visual handicap limits vision to 20/200, or one-tenth of normal, a person is legally blind. Legally blind does not mean totally unable to see. Someone legally blind cannot see the line below the second big E at the top of the eye chart. People with 20/20 vision but less than 20 degrees of side vision can also qualify as legally blind. People who see well with only one eye are not considered legally blind, nor are people who wear glasses to see better than 20/200.
Most legally blind people function quite well, especially if they have been visually handicapped since childhood. Older children and adults with visual handicaps may need magnifying lenses for reading and telescopes for distance viewing. People with very poor vision may need to learn Braille and walk with a seeing-eye dog or a cane.
Young children with visual impairments should have help from a teacher of the visually impaired and should be evaluated for developmental problems by professionals experienced with visual handicaps. Parents may need to be advocates for their child to obtain needed services through the school system.
Visually handicapped people of all ages benefit from social service, occupational therapy, and orientation and mobility training. Many new devices are available to cope with vision loss, including books on audio tapes, scanners that turn print into Braille, watches that can be “read” with the fingers, and talking computers and calculators.
Over three million people in the United States do not have normal vision even with corrective lenses. If ordinary eyeglasses do not provide clear vision, one is said to have low vision. This should not be confused with blindness. People with low vision still have useful vision that can often be improved with low-vision devices.
Low vision can result from birth defects, inherited diseases, injuries, diabetes, glaucoma or macular degeneration. Although reduced central or reading vision is most common, a person can have low vision in their side (peripheral) vision or a loss of color vision or contrast sensitivity.
Low vision devices or aides are available in optical and non-optical types. Optical devices use lenses or combinations of lenses to provide magnification. They should not be confused with standard eyeglasses. There are five main kinds of optical devices: magnifying spectacles, hand magnifiers, stand magnifiers, telescopes and closed-circuit television. Different devices may be needed for different purposes. If possible, try the optical device before purchasing it and be sure you understand how to use it.
The simplest non-optical technique is to bring the object of interest closer. Non-optical low vision devices include large print books, check writing guides, enlarged phone dials, talking appliances (timers, clocks, computers), and machines that scan print and read out loud.
Government and private agencies have social services available for people with low vision. For more information, contact the following resources: