What is age-related macular degeneration (AMD)?
AMD is an eye disease that is estimated to affect more than 800,000 Canadians. It causes damage to a very small but important part of the retina called the macula. Although it is only about the size of a pencil tip, the macula contains the millions of cells needed for straight-ahead vision and for seeing fine details and colour. As its name indicates, AMD is more likely to affect people in their senior years, and it is the leading cause of legal blindness in Canadians over the age of 60.
There are two basic types of AMD: "wet" and "dry". The dry form is more common accounting for 90 per cent of all AMD cases. During an eye examination the eye doctor will observe a buildup of small, yellowish deposits beneath the macula. These deposits, called drusen, indicate that the light-sensing cells in the macula are weakening. The result is a slow, progressive loss of central vision.
The wet, or exudative, form of AMD is a much more serious condition. An underlying network of tiny blood vessels nourishes the light-sensing cells of the macula. If the macula has become thin and weakened by accumulations of drusen, these blood vessels may break through. Sometimes these blood vessels grow abnormally, become fragile and leak blood and fluid under the macula. The resulting damage can lead to the rapid loss of central vision.
Although only approximately 10 per cent of all people with AMD have the wet form, it accounts for 90 per cent of all legal blindness due to the disease.
What causes AMD?
The causes of AMD are unknown. Some studies have shown familial patterns of the disease, which suggest there may be genetic causes. Although a specific inheritance pattern has not been identified, it is estimated that 15 to 20 per cent of AMD patients have one or more close relatives who are also affected.
Can AMD be prevented?
At present, there is no proven way to prevent AMD.
Will AMD cause total blindness?
No. Although AMD is a leading cause of vision loss, and some people with AMD become legally blind, most keep their peripheral vision. This allows them to stay active, mobile and independent.
At what rate will I experience vision loss?
The rate at which AMD causes vision loss varies greatly. Sometimes the disease advances so slowly that it will have little effect on your vision as you age. In others, the disease progresses more quickly, and may lead to vision loss in one or both eyes. Wet AMD tends to progress more rapidly than the dry form.
Are cataracts associated with AMD?
A cataract is a clouding of the lens of the eye. It is not uncommon for an older individual with AMD to also develop cataracts. Cataracts that significantly interfere with vision can be surgically removed. While cataract surgery can restore vision reduced by the cataract, it does not improve vision loss caused by AMD.
If AMD is incurable, what good are checkups?
Having your eyes checked regularly is an essential part of your personal health care program. This allows early detection and diagnosis of not only AMD, but of other eye diseases. Keep in mind that a small but significant number of patients with AMD have found that laser treatment has stabilized their vision loss. Your ophthalmologist will also keep you informed of the latest developments in treatments as they emerge.
Will AMD affect my ability to drive?
Many people with mild forms of AMD continue to drive legally and without any difficulty. For others, however, this is not the case. Vision loss should be discussed with a physician who can assess whether your visual function passes legal standards.
Many people equate driving with independence. It is often hard for people to acknowledge that they have a visual impairment, and that it affects their driving skills. It is important to remember that your ability to operate a motor vehicle safely not only impacts you, but also pedestrians and other drivers.
Will AMD affect my daily living?
There are a number of aids available to help people with AMD manage daily life with vision loss.
Non-optical aids include audiotapes and large print books, magazines and newspapers. There are also a number of optical aids which, may help improve vision. These include Corning and Noir glasses, telescopes and magnifiers.
Electronic aids include closed-circuit television (CCTV), reading machines, and talking computers. An increasing number of computer programs are making it easy to enlarge the typeface or provide an audio version of what appears on the monitor. Advances in technology continue to create new opportunities for people with AMD to maximize the use of their remaining vision.
For information on orientation and mobility training, as well as other services and techniques, please contact your local CNIB or provider of low vision services.
This information has been provided by The Foundation Fighting Blindness - Canada and has been reviewed by its medical advisor. It is not intended to replace the advice of a qualified vision care professional. The Foundation urges everyone affected by an eye disorder to seek the best healthcare possible.