Understanding Visual Impairment
There are approximately three million people in the United States who do not have normal vision even with corrective lenses. These individuals are considered visually impaired. The many causes for impaired vision include cataracts, glaucoma, diabetic eye disease, macular degeneration, eye injuries and inherited eye diseases. Although your ophthalmologist can diagnose and treat many eye disorders, some may progress, causing avoidable loss of central (reading) vision, peripheral (side) vision, or both.
Federal guidelines have defined a certain level of visual impairment as "legal blindness". A person who is legally blind may not be totally blind and may still have some useful vision. The central vision is usually measured using an eye chart with the results recorded as a pair of numbers called the "visual acuity." In the familiar 20/20 notation, the first number is the testing distance measured in feet and the second number is the distance from which a normal eye should see the letter clearly. A person with 20/20 vision can see certain sized letters at a distance of 20 feet. An individual with a visual acuity of 20/60 can only see at 20 feet the same size letters which a healthy eye can identify at 60 feet. The larger the second number, the lower the visual acuity. Side vision can also be measured in the ophthalmologist’s office.
Normal eyes can visualize objects over an area measuring at least 140 degrees (almost half a circle). A person with reduced peripheral vision may be unable to walk safely or recognize people in a large room, even though his or her central vision is excellent. When the best corrected central visual acuity is 20/200 or worse in the better eye, or the side vision is narrowed to 20 degrees or less in the better eye, one is considered legally blind even though they may still have some useful vision. People with this degree of impairment may qualify for certain government benefits and receive assistance from public and private organizations. If neither eye can see better than 20/60 without improvement from eyeglasses or corrective lenses, the individual is defined as visually impaired.
A variety of visual rehabilitation programs, devices, and supportive services are available for the visually impaired. An ophthalmologist can refer them to the appropriate state and local agencies for the visually disabled, where they can obtain a handicapped parking designation, low-vision services, and possibly Social Security and Department of Veterans Affairs benefits. Federal and state income taxes can be reduced through an extra exemption allowed to “legally blind” individuals. Some communities may offer a reduction in property taxes as well.
Visually impaired individuals should continue seeing their ophthalmologist for regular checkups. Their eye disorder may change, so its treatment may also need to be changed. Because eyes can be affected by more than one disease, it is especially important that any new problems be detected and treated promptly in order to preserve any remaining sight.
