National Eye Institute
This is an Amsler grid. With normal vision,
the grid would appear as straight lines while staring at the dot (see top sample). If the lines appear wavy, as bottom sample, it may be a sign of AMD. Visit www.nei.nih.gov and search for macular degeneration.
Health
June 23, 2008 03:17 PM
beingwell magazine Summer 2008
By: Robin Harvey
Age-related macular degeneration (AMD), which slowly destroys sharp central vision but usually leaves peripheral vision intact, is the most common form of blindness in people over 60, however it can also strike those in their 50s. But with new research and treatments, things are looking much brighter for the estimated one million Canadians who have some form of the painless, but devastating disease, according to Dr. Eugene Liu, an ophthalmologist at Southlake, who also lectures at the University of Toronto.
There are two types of AMD — the wet type and the dry type. Dr. Liu says roughly 80 per cent of cases of AMD are the dry form and 20 per cent are the wet form.
However, the wet form causes 80 per cent of vision loss.
Wet AMD occurs when abnormal blood vessels behind the retina, the light sensitive tissue at the back of the eye, grow under the macula, the part that lets you see fine detail. These new blood vessels are fragile and leak, damaging the macula. Central vision loss can occur quickly and treatment is crucial, Dr. Liu says.
The newest treatment for the wet form involves using a drug called Lucentis. “It changes the property of blood vessels,” Dr. Liu says. “Lucentis inhibits the growth of abnormal blood vessels and thereby allows the fluid and hemorrhaging to resolve, possibly restoring vision. Unfortunately, injections every four to six weeks are required.” If started before the blood vessels cause scarring, the Lucentis treatment may reverse vision loss.
Another method of treatment for wet AMD is photodynamic therapy, which is used to destroy the fragile, leaky blood vessels. With photodynamic therapy, a drug called Verteporfin is injected into the vein and eventually reaches and binds to the abnormal vessels. Light is then shone into the eye, activating the drug which then destroys the abnormal vessels, slowing the decline in vision.
Photodynamic therapy has been supplanted largely by Lucentis, which has been found to be far more effective.
Dry AMD occurs when light-sensitive cells in the macula slowly break down, blurring central vision. As it gets worse, the centre of your vision may have a blurred spot. Gradually, central vision is lost in the eye and may similarly affect the other eye. Slightly blurred vision and trouble recognizing faces, needing more light to read or for other tasks, are signs of dry AMD.
One common early sign of dry AMD are drusen. Drusen are yellow deposits under the retina, often found in people over 60 and can be detected during a comprehensive dilated eye exam. But an increase in the size or number of drusen raises a person’s risk of developing either advanced dry AMD or wet AMD.
For people with dry AMD, studies have shown taking a specific high-dose formulation of vitamins, antioxidants and zinc slows the progression of the disease, Dr. Liu says.
Varieties of the formulation, called AREDS (named for the study that developed it, Age Related Eye Disease Study), are sold at drugstores and many patients may try them on their own.
But Dr. Liu says such high levels of vitamins may be toxic and should be taken only with medical supervision. They may cause side effects, may interfere with other medications and have been linked to increases in lung cancer in smokers.
Patients should keep their family doctor informed if they start taking these vitamins.
A healthy weight, diet and exercise, keeping blood pressure controlled, avoiding too much UV eye exposure and not smoking, are crucial to preventing AMD, as well as getting regular eye exams.
For more information on AMD call 1-877-AMD-7171 (U.S./Canada) or visit www.amdalliance.org