What is Macular Degeneration?
Age-related macular degeneration (AMD) is the most frequent cause of vision loss in people over age 50 in developed nations. Its destructive effects involve the very center of vision, making it difficult or even impossible to read, drive or recognize faces.
There are essentially two basic forms of this disease: the dry (atrophic) type and the wet (neovascular type). In dry AMD, cells living beneath the retina in the center of vision (the macula) simply wither and fade away, causing retinal function to decline. At this time, there is no effective treatment for this form of AMD. In wet AMD, abnormal blood vessels and scar tissue grow beneath the retina, causing a decline in central vision. Although there is no permanent cure for this form of AMD, there are a number of available treatment options.
Schematics of Macula
Treatment Strategies for Macular Degeneration (Wet):
Surgical treatment options either involve moving the retinal center of vision to a new location within the eyeball, away from the underlying patch of abnormal blood vessels and scar tissue (macular translocation), or removing the abnormal complex of vessels and scar tissue from underneath the retina using a small retinal incision (submacular surgery) or a combination of the two. Although preliminary data were initially encouraging, the long-term benefits of such interventions are questionable.
Laser treatment options include thermal (hot laser) destruction of the underlying abnormal blood vessel complex, non-thermal (cool laser) destruction of the abnormal blood vessel complex, and focal destruction of selected blood vessels that feed the complex (feeder vessel laser). Since the hot laser treatment produces a full thickness burn involving both the abnormal blood vessels and healthy overlying retina, its use is now reserved for cases in which the abnormal blood vessels do not yet involve the very center of vision. Cool laser treatment involves injection of a unique and highly selective photosensitizing dye, which collects in the abnormal blood vessel complex beneath the retina. This dye is then activated by application of the cool laser, causing more selective destruction of the underlying abnormal blood vessels while sparing the overlying healthy retinal tissue. Cool laser treatment, also known as photodynamic therapy (PDT) has recently been shown to be effective in reducing vision loss in wet AMD, but only a minority of patients have improvement of vision. Many patients still lose vision, but much less than they would if their macular degeneration were to have gone completely untreated. Feeder vessel laser treatment has promise, but more controlled clinical data are needed to determine its long-term benefit.
Exciting progress has been made in the treatment of wet AMD with the recent development of medications that can block the growth of abnormal blood vessels in the macula. These medications are placed in the eye with a microsurgical needle in the office with minimal discomfort. Early clinical data suggest that eyes treated in this fashion have a high chance of stabilizing without further vision loss with a significantly higher chance of gaining back vision than patients treated with PDT. It is important to emphasize that although the data are encouraging, we do not yet have long-term experience with this treatment. Additionally, there is a small chance that this form of treatment can lead to complications such as infection, bleeding, lens injury and retinal detachment.
Vitamin and Mineral Supplements and Macular Degeneration
Results from the Age-Related Eye Disease Study (AREDS), a federally funded study sponsored by the National Eye Institute (NEI), indicate that high-dose antioxidants and zinc can reduce the risk of vision loss in advanced macular degeneration by about 19 percent in patients who were determined to have high-risk macular degenerative change.
It is important to note that high-dose vitamin supplements are of no benefit to patients with minimal macular degenerative change. Vitamins also do not prevent the development of macular degeneration nor can they restore vision that has already faded due to macular degeneration.
The vitamins and dosages used in the study were as follows:
- Vitamin C 500 mg
- Vitamin E 400 IU
- Beta-carotene 15 mg
- Zinc 80 mg, as zinc oxide
- Copper 2 mg, as cupric oxide (Copper must be supplemented with high dose zinc because high dose zinc can lead to copper deficiency)
Smokers and former smokers are advised not to take beta-carotene due to a link between this vitamin and lung cancer among smokers found in some research studies. In addition, patients on blood thinners are not advised to take vitamin E, which may increase the risk of bleeding.
It is important to remember that there is no absolute cure for AMD. Even our most sophisticated options at this point are not able to restore vision; they can only slow down the rate of decline over time. Fortunately, there is a tremendous amount of aggressive research into new treatment options, such as cell transplantation, genetic-based therapies, newer pharmacologic agents, radiation, new laser technology and computer chip prosthetic implants.
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