Low vision is a term used to describe having impaired but some useful vision that that cannot be fully corrected by conventional eyewear, surgery or medical treatments. More than 13 million Americans have some degree of low vision -- often a loss in visual sharpness or acuity. However, low vision may also include a loss in the general field of vision, increased light sensitivity, distorted vision, a loss in contrast or other impairments that affect the quality of life and the ability to do everyday activities.
People with low vision are not blind, although many are classified as being "legally blind" -- a term used to describe visual acuity no better than 20/200 in the better eye with visual correction such as eyeglasses or contact lenses. This means that they must be 20 feet away to clearly see an object that a person with 20/20 eyesight can see clearly from 200 feet away. "Partially sighted" is the other general classification associated with low vision and refers to a visual acuity between 20/70 and 20/200 in the better eye with the best-corrected lens in place.
Low vision often occurs from complications of eye diseases such as
cataracts, retinal lesions or
glaucoma. It can also result from stroke, eye or head injuries, brain tumors, birth defects or even the natural aging process. Although low vision cannot be cured, there are various devices and adaptive products to help you live a more productive and safe life. Many of these devices -- along along with counseling and other rehabilitative therapies -- are specifically prescribed on a case-by-case basis by an eyecare provider.
Any difficulties in seeing -- whether it's recognizing a familiar face, trouble reading or seeing objects such as furniture or walls -- could be symptoms of low vision. Other symptoms include:
- Blurred or distorted vision
- Central or multiple field loss, in which a dark hole, patches or hazy area appears in the center or around objects
- The loss of peripheral vision, in which objects in the center of vision appear clear but those on the sides are blurry
- Light sensitivity or glare
- A loss in contrast, in which objects blend in with their surroundings
Since low vision often results from eye and other diseases, prevention may occur by quick management of those conditions.
A thorough eye exam by your eyecare providers that includes a comprehensive health history is necessary to determine the possible cause of your low vision, and help determine which specific optical and non-optical devices may be most useful to you.
Optical devices include but are not limited to:
- Magnifiers that can be held or mounted onto eyeglasses or on a special headband that help for reading, writing, sewing, and other "close" activities.
- Spectacle-mounted telescopes that are useful for seeing longer distances, such as across the room to watch television.
- Closed-circuit television (also called CCTVs) that enlarge reading material on a video screen. Some are portable, while some can be connected to a computer. The user can adjust the image brightness, size, contrast and background illumination.
Non-optical devices include products such as large-print reading material, check-writing guides, enlarged telephone dials, high contrast watch faces, self-threading needles, "talking" computers, clocks and other products, and special lighting to reduce glare.
In addition to products, your eyecare provider may recommend resources that provide social services to those with low vision, counseling to deal with emotional effects, or occupational therapists that come to your home to help you make it safer and more efficient.