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Normal vision, or 20/20 vision, means that a person can read the smallest letters or see the pictures on an eye chart when standing 20 feet away from the chart. Some people cannot see normally even with eyeglasses or contacts because a medical condition affects their vision. These people are called visually impaired or visually disabled.
If a visual impairment limits vision to 20/200, or one-tenth of normal vision in their better seeing eye, a person is considered legally blind. Being legally blind, however, does not mean a person is totally unable to see. People with 20/20 vision but less than 20 degrees of side (peripheral) 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 impaired since childhood. Older children and adults with visual impairments 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 disabilities should have help from a teacher of the visually impaired and should be evaluated for developmental problems by professionals experienced with visual impairments. Parents may need to be advocates for their children to obtain needed services through the school system.
Visually impaired people of all ages benefit from social service, occupational therapy, and orientation and mobility training. Many new devices are available to help them cope with vision loss, including books on audiotape, scanners that can turn print into Braille, watches that can be “read” with the fingers, and “talking” computers and calculators.
Low vision is loss of eyesight that makes everyday tasks like reading, writing, crossing the street, or watching television difficult. When vision cannot be improved with eyeglasses, medicine, or surgery, people with low vision need to know how to best maintain their existing vision and best utilize the vision they still have. With a little help, they can live very active, productive lives.
Low vision can affect central or peripheral vision, depth of perception, or visual processing.
Low vision may be caused by eye injuries or conditions such as age-related macular degeneration, glaucoma, diabetic retinopathy, or retinitis pigmentosa.
Vision rehabilitation can help people with low vision. You can learn new strategies to complete daily activities, regaining confidence in your ability to live independently despite vision loss.
There are many low vision aids available, such as magnifying spectacles, hand and video magnifiers, and telescopes, that can help you make the most of your remaining vision. Learning to adjust lighting appropriately can often improve your vision for reading, cooking, dressing, and walking up and down stairs.
What can you do to prevent vision loss? Early examinations can help reduce the risk of vision loss. If you are experiencing difficulty seeing, it is very important to visit your ophthalmologist (Eye M.D.) immediately to get a comprehensive examination. Diagnosis and possible treatment of your eye condition may slow progression of the vision loss and in some cases can improve vision.
A low vision examination may also be helpful. Rehabilitation may be possible. A low vision examination differs from a normal eye exam in that it is typically longer and involves a number of tests that you may not be familiar with.
Typically, the ophthalmologist reviews your medical and ocular history and then asks you for detailed information about your vision problems and how they are affecting your everyday life.
After taking your history, your ophthalmologist will do a number of tests to assess your vision. These tests may include:
Having frequent eye examinations helps to ensure that your eyes will remain as healthy as possible. If you are experiencing difficulty with your vision, it is important to see your ophthalmologist right away. A comprehensive eye examination can catch eye-related problems early and help reduce vision loss.