Low vision is the loss of sight that is not correctable with prescription eyeglasses, contact lenses, or surgery. Low vision does not include complete blindness, because there is still some sight. Low vision can be treated or offset, however, with the use of vision aids such as magnifying glasses.
Low vision includes different degrees of sight loss -- from having blind spots to almost a complete loss of sight. The American Optometric Association divides low vision into two categories based on the vision in the best eye:
Pterygium (pronounced tur-IJ-ee-um) is a common eye condition that affects people who spend a lot of time outdoors. People with pterygium have a growth of pink, fleshy tissue on the white of the eye. It usually forms on the side closest to the nose.
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1. Partially sighted, meaning the person's vision is between 20/70 and 20/200 with conventional prescription lenses
2. Legally blind, meaning the person's vision is no better than 20/200 with conventional correction or a restricted field of vision less than 20 degrees wide
Low vision is a result of a variety of conditions and injuries, but age is a factor. Macular degeneration, glaucoma, and cataracts are more common in people over age 45 and even more so in adults over age 65: One in six adults over age 45 has low vision, and one in four adults over age 65 has low vision.
The most common types of low vision include:
Loss of central vision. A condition in which there is a blind spot in the center of one's vision
Loss of peripheral (side) vision. An inability to see anything to either side and above or below eye level. Central vision, however remains intact.
Night blindness. An inability to see in poorly lit areas such as a theater, as well as outside at night
Blurred vision. A condition in which objects both near and far appear out of focus
Hazy vision. A condition in which the entire field of vision appears to be covered with a film or glare
What Causes Low Vision?
Besides age, there are many other possible causes of low vision, including conditions such as diabetes. Low vision may also result from cancer of the eye, albinism, stroke, or a brain injury. If you have or are at risk of having these disorders, you are at an increased risk for low vision.
How Is Low Vision Diagnosed?
An eye exam by an eye care specialist can diagnose low vision. You should make an appointment with your eye doctor if your vision difficulties are preventing you from daily activities like reading, travel, cooking, work, watching television, and school. The tests the eye doctor will perform include the use of lighting, magnifiers, and special charts to help test visual acuity, depth perception, and visual fields.
Can Low Vision Be Treated?
Some sight disorders, like diabetic retinopathy, can be treated to restore or maintain vision. When this is not possible, low vision is permanent. However, many people with low vision find visual aids helpful. Popular low vision aids include:
Lenses that filter light
Hand-held and freestanding magnifiers
Closed-circuit television/video magnification
Non-optical aids designed for people with low vision are also very helpful. Some popular non-optical devices include:
Text reading software
Check writing guides
High contrast clocks and watches
Talking watches and clocks
Clocks, phones and watches with enlarged numbers
Books on DVD/audiocassette
Visual aids improve both sight and the quality of life for many people. Talk to your health care provider about where to purchase visual aids.
Can Low Vision Be Prevented?
Low vision may be prevented for patients with diabetes and reversed for those whose vision loss is caused by cataracts.