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Michael
Pinnolis, MD, discusses Macular Degeneration
 Macular
degeneration, in most cases is a slowly progressive disease. It
gradually causes a loss of the photoreceptor cells of the central
retina leading to worsening of vision. If the damage is limited to
the loss of cells, then the patient is said to have "dry"
macular degeneration. Sometimes abnormal vessels begin to grow
underneath the macula, in the area of degeneration. This is a process
called choroidal neovascularization, and the blood vessels themselves
are referred to as a choroidal neovascular membrane (CNVM).
It appears there are at least two reasons why these vessels grow into the degenerated areas. The healthy retinal cells, which would normally prevent abnormal blood vessel growth, are no longer present. And, blood vessel growth is stimulated by the presence of certain protein factors that encourage these blood vessels to grow. These chemical substances are known as angiogenic growth factors. If abnormal blood vessels are present, they may leak fluid or blood underneath the retina.
This condition is known as "wet"
macular degeneration. Wet macular degeneration is potentially worse
than dry age-related macular degeneration because the blood vessels
may continue to grow, destroying a far larger area of the central
retina than that caused by dry degeneration alone.
The underlying tissue complex of blood vessels and fibrous support tissue may form a large scar under the retina. In wet degeneration, the retina may swell,
which then causes the distortion of lines seen on the Amsler grid.
"Dry" and "wet" macular degeneration are not two
separate diseases.
The "wet" form is simply a complication or more advanced form of the disease. Anyone with "dry" macular degeneration must
be examined periodically to be sure they are not progressing to the
"wet" form.
Nutrition (Prevention)
A major national trial called the Age Related Eye Disorder Study (AREDS) sponsored by the National Institutes of Health and National Eye Institute, looked at several thousand people with macular degeneration. Patients in the trial took either certain vitamins or a placebo (sugar pill), and neither the patients nor the doctors knew what they were taking. At the end of the study period, the patients who took the high dose vitamins did far better than the patients who took the placebo. The tested nutritional factors were Beta-carotene, Vitamin C, Vitamin E, and Zinc. However, you should discuss the appropriate formula for vitamin therapy with your ophthalmologist. The therapeutic dosage for these supplements is very high. There are potential side effects, and not everyone will benefit from this regimen. The study continues, and other supplements (lutein, zeaxanthine) are under investigation as well. Another nutrition supplement, Omega 3 fatty acids, has been strongly associated with lower levels of macular degeneration. Omega 3's are found in oily fish, fish oil capsules and flax seed oil. Some nutritional supplements are popular in alternative medicine such as bilberry, which is a powerful antioxidant. But there are no good, scientific studies looking at the effectiveness of these other supplements.
Treatment
Dry Macular Degeneration
There is currently no guaranteed treatment for "dry" macular degeneration, but some interventions have been shown to be helpful. Treatment strategies have been directed at several areas and much research is currently taking place.
Wet Macular Degeneration
Thermal Laser: The presence of abnormal blood vessel growth is the most devastating complication of macular degeneration. A great deal of work has been directed at treating this problem. Thermal laser ("hot" laser) treatment has been successfully used to burn out abnormally growing blood vessels and prevent deterioration of vision due to "wet" age-related macular degeneration. The laser is done in an office setting and takes only a few minutes. The laser beam is microscopic and there is no pain involved in this treatment. Unfortunately, only a few patients meet the very strict criteria for successful laser treatment: i.e. the abnormal blood vessels must be easily seen on photographic testing, and they must not be directly in the center of the macula. Treating the center of the macula with laser burns the visual cells and causes a permanent blind spot and loss of vision. Therefore, only blood vessels away from the exact center of the retina may be treated.
Central Wet Macular Degeneration
Photodynamic Therapy (PDT): Photodynamic therapy or PDT works in some situations where thermal laser cannot be used. The theory behind the treatment is to use such a low dose of laser, that it will not be harmful to the central retinal cells and therefore preserve vision. The laser dose used is too weak to be helpful under normal circumstances, but just prior to treatment, a special dye (Visudyne®) is injected into the blood stream. Visudyne® absorbs the laser energy, undergoes a chemical reaction and causes the blood vessels to coagulate. The dye enhances the laser effect only on these abnormal blood vessels, destroying them while at the same time preserving the delicate retinal visual cells. Several trials have shown that Visudyne® works in many cases to prevent further deterioration of vision, but only a few patients improve their vision. Recent studies have suggested that the additional injection of a steroid (cortisone-like drug), Kenalog®, can augment the effect of PDT and may improve vision. The effectiveness of steroids remains uncertain at this time.
New Medical Treatment:
By far the most exciting and promising modalities for treatment of wet macular degeneration are the new biologic therapies. There are new steroid-like drugs that are now being tested in ongoing trials. These steroids are designed to be more effective and have fewer side effects than current steroids. Drugs currently in testing include Retanne® and Posurdex®.
Another class of drugs works by blocking the vascular growth factors that stimulate the blood vessel growth seen in wet macular degeneration. Sometimes called anti-VEGF drugs, they offer promise of a significant improvement in the treatment of abnormal blood vessels. One such drug Macugen®, has been shown in clinical trials to be effective in slowing or stopping macular degeneration, and it was approved for use by the FDA in wet macular degeneration in 2005. Macugen® seems to have some effect in improving vision as well as stablizing vision. It must be administered as an injection into he eye itself every 6 weeks. Another drug, Lucentis®, is in the late stages of a Phase 3 trial, and shows great promise, but it is not yet available to the public. Lucentis® also must be administered via intra-ocular injection, in this case once a month.
Low
Vision
Macular
degeneration is a very frustrating disease. Although it is often not
possible to prevent some vision loss in age-related macular
degeneration, one can still have a productive life. Low vision aids
are available to enable people with macular degeneration to better
utilize their remaining vision. These aids and devices are varied and
may involve the use of magnifying lenses or glasses, small
telescopes, large print books and large print appliances, closed
circuit TV enlargers, etc. If your vision is poor due to macular
degeneration, you may want to consider a referral to a low vision
specialist. This is a doctor who can work with you to help you get
the most out of your remaining sight.
Dr.
Michael Pinnolis is a Retina Specialist and practices in the
Retina Service in Kenmore Visual Services of Harvard Vanguard Medical Associates.
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