What is low vision?
Low vision is decreased vision that cannot be corrected with glasses, contact lenses, medication, or surgery. People who cannot see better than 20/200 are often said to have low vision. (A person with 20/200 vision can see something 20 feet away that a person with normal vision can see 200 feet away.)
People with low vision are not blind. However, they have vision problems that may include:
- a loss of clear central vision
- reduced visual field (the area visible around the object that you are looking at directly)
- a loss of color vision
- a loss of the ability to adjust to glare
- the need for greater contrast.
How does it occur?
Low vision is caused by damage to part of the visual system. The visual system includes the cornea, lens, retina, optic nerve, and vision centers in the brain. This damage can be the result of:
- birth defects
- diseases such as diabetes
- severe high blood pressure
- eye injuries
- a cataract or cloudy lens in the eye.
One of the most common causes of low vision is age-related macular degeneration (a problem with the part of the retina that allows us to see detail in the center of our field of vision).
What are the symptoms?
Symptoms may include:
- trouble reading and seeing small objects
- blurry or spotty vision
- loss of peripheral (side) vision
- loss of depth perception
- the need for bright light most of the time.
How is it diagnosed?
Your eye doctor will give you a complete eye exam. He or she will also ask about your medical history because many diseases may affect your eyes.
How is it treated?
Because low vision cannot be treated with ordinary glasses or contact lenses, you will probably use devices to help you with your daily activities. Low-vision aids fit into two broad categories: optical and nonoptical.
What are optical devices and how do they help with low vision?
Optical devices make things look larger. They include:
- Magnifying eyeglasses, which are like regular eyeglasses, but they make things look even larger. With these eyeglasses, you may need to hold your reading material or objects close to your eyes to get it in focus.
- Hand-held magnifiers, which you can buy at drug stores and at low-vision centers. They come in many shapes and sizes.
- Stand magnifiers, so that you do not need to hold anything over your reading material or other objects. They may have their own light source.
- Telescope eyeglasses, which make things at distance look larger than regular glasses do. Each side has two lenses that are separated by a small space.
- Closed-circuit TV, which magnifies and sharpens the contrast of images on a TV screen.
What are nonoptical devices and how are they used to treat low vision?
Non-optical devices are things other than magnifiers that can be used easily by people with low vision. Examples are:
- large-number phone keypads
- large-numeral watch faces
- filters that reduce glare
- "talking" clocks or scales
- books, magazines, or newspapers on tape or printed in large type.
Many electronic aids can help people with low vision. Some of these are:
- Personal computer hardware and software that enlarge images on a computer screen. These can often be used with closed-circuit TV.
- Systems that use video cameras and large TV screens to enlarge reading material.
- Machines that "read" printed material aloud in a computer voice.
Where can people with low vision go for help?
Start with your eye doctor. He or she will recommend treatment or products that may help you. Sometimes your eye doctor will refer you to a low-vision center or specialist for additional help.
How can I take care of myself?
Learn what you can about low vision devices that may help you. If you can, try out a product before you buy it. Also, remember the simple things you can do to help you see better:
- Sit close to the TV or hold reading material close to your eyes.
- Use enough light. A person with no eye problems needs about twice as much light at age 60 as he or she did at age 20 for the same task. Also, wear a visor to block overhead light or special lenses to reduce glare.