More than three million people in the United States do not have normal vision, even with the help of eyeglasses or corrective lenses.
These individuals are considered visually impaired. Visual impairment may be caused by a number of eye diseases, including age-related macular degeneration, diabetic retinopathy, glaucoma and cataracts. Visual impairment may also be caused by trauma or inherited eye disorders.
Although many eye diseases can be treated by your ophthalmologist (Eye M.D.), some may result in the unavoidable loss of central vision (used for reading/detail work) or peripheral (side) vision—or both.
Visual impairment can range from mild to severe. Federal regulations define a certain level of visual impairment as legal blindness, which should not be confused with total blindness. Most of the approximately one million Americans defined as legally blind keep some useful vision.
HOW IS SIGHT MEASURED?
To understand the definition of visual impairment and legal blindness, you need to know how your eyesight is measured. Central vision is measured using an eye chart. The results are recorded as a pair of numbers called visual acuity. Normal sight is scored as 20/20. The first number is the distance from the eye chart. The second number is the distance from which a normal eye sees a letter on the chart clearly. Someone with a visual acuity of 20/20 can see certain sized letters at a distance of 20 feet. Someone with a visual acuity of 20/60 only sees letters at 20 feet that a normal eye identifies at 60 feet. The higher the second number of your visual acuity, the worse your vision will be.
Peripheral (side) vision is measured with an instrument called a perimeter. Using targets of different sizes and brightness, a perimeter measures the total area that you can see while looking straight ahead. The results are recorded in degrees. In a normal eye, peripheral vision is 180 degrees. A person with a much narrower range of side vision may have trouble walking, recognizing people in a large room or driving a car—even when his or her central vision is excellent.
Your ophthalmologist may also administer other tests to measure your level of visual function. These include tests of eye movement, color and contrast vision, three-dimensional vision, and adjustment to light and dark.
WHAT IS LEGAL BLINDNESS?
When your visual acuity with eyeglasses or corrective lenses is 20/200 or worse, or your side vision is 20 degrees or less, you are considered legally blind—even though you may still have some useful vision. You may qualify for certain government benefits or receive assistance from public and private organizations if you are legally blind.
WHAT IS VISUAL IMPAIRMENT?
If your vision with eyeglasses or corrective lenses is 20/60 or worse, you are considered visually impaired. Limitation of side vision, abnormal color vision, or presence of double vision in one eye may also determine visual impairment.
WHAT IS A VISUAL DISABILITY?
If you cannot perform certain tasks because of your visual impairment, you are considered “visually disabled.” An exact rating or quantification of the disability is necessary to receive worker’s compensation, insurance disability benefits, legal claims, or certain forms of government assistance.
Visual disability is expressed in percentages to determine how much the whole person is disabled by his or her visual handicap. For example, total loss of vision in both eyes is a 100% disability of vision, but only an 85% disability of the whole person.
WHAT CAN I DO ABOUT MY VISUAL IMPAIRMENT?
- Schedule regular eye examinations with your ophthalmologist to monitor your eye health and your remaining vision. Your eyes can be affected by more than one condition, so it is important that any new problems be diagnosed and treated promptly in order to preserve your remaining vision.
- Ask your ophthalmologist about low-vision resources. There are many rehabilitation services and devices for people with reduced vision, including counselors, large and high contrast print materials, audio publications and materials, optical and electronic magnifiers, mobility training, and improved lighting devices.
- Join a support group for people with similar eye problems.
- Ask your ophthalmologist to refer you to the appropriate state and local agencies for the visually impaired. These agencies can help you obtain handicapped parking, low-vision services, Social Security and Department of Veterans Affairs benefits, or information about federal and state tax exemptions for the visually impaired.