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Low vision affects 20% of middle-aged adults, but often this condition can be treated or offset by new vision aids.

Low vision is the loss of sight that is not correctible with prescription eyeglasses, contact lenses, or surgery. Low vision does not include complete blindness because there is still some sight. Often low vision can be improved with the use of visual aids.

Low vision includes different degrees of sight loss from having blind spots, poor night vision, and problems with glare to almost a complete loss of sight. The American Optometric Association defines low vision into two categories:

1. Partially sighted, meaning the person has visual acuity between 20/70 and 20/200 with conventional prescription lenses
2. Legally blind, meaning the person has visual acuity no better than 20/200 with conventional correction and/or a restricted field of vision less than 20 degrees wide

The ratio measurement of vision describes visual acuity, or the sharpness of vision, at 20 feet from an object. For example, having 20/70 vision means that you must be at 20 feet to see what a person with normal vision can see at 70 feet.

Anyone can be affected by low vision because it results from a variety of conditions and injuries. Because of age-related disorders like macular degeneration, glaucoma, and cataracts, low vision is more common in adults over age 45 and still even more common in adults over age 75. One in six adults over age 45 have low vision; One in four adults over age 75 have low vision.

The most common types of low vision include:

• Loss of central vision. A condition in which a blind spot in the center of one's vision
• Loss of peripheral (side) vision. Inability to see anything to either side, above or below eye level. Central vision, however remains intact.
• Night blindness. The inability to see in poorly lit areas such as a theater, as well as outside at night
• Blurred vision. A condition in which object 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?

There may be one or more causes of low vision. Low vision is usually the result of disorders or injuries affecting the eye -- or a condition such as diabetes that affects the entire body. Some of the most common causes of low vision include: age-related macular degeneration, diabetes, and cataracts, but low vision may also result from cancer of the eye, albinism or a brain injury. If you have or are at risk of having these disorders, you are at an increased risk for having low vision.

How Is Low Vision Diagnosed?

An eye exam by your 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 travel, cooking, work, 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 field.