Age-related macular degeneration (AMD)

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What is Age-related macular degeneration (AMD)?

AMD is the most common cause of legal blindness among older Americans. As the name implies, this condition is characterized by degeneration of the macula (the central retina) associated with aging. Within the last few years, great strides have been made in the understanding of AMD giving promise that effective treatments might be forthcoming in the near future.

Individuals with AMD may notice blurring, blind spots, and/or distortion affecting the central vision. Alternatively, they may be completely symptom-free. The examining doctor may see yellow deposits under the retina (drusen), pigmentary alterations, or patches of atrophy (thinning or loss of tissue). These findings are the hallmarks of atrophic (dry) AMD which accounts for 90% of patients with the disease. An unfortunate minority of individuals with AMD develop the growth of abnormal blood vessels under the retina (choroidal neovascularization). The vessels may leak fluid under the retina or bleed causing a decline in central vision. Left untreated, choroidal neovascularization will usually form a scar under the macula which corresponds with a blind spot in the affected individual’s vision. Fortunately, it is quite uncommon for AMD to affect the peripheral retina. Complete blindness from the condition is thus quite rare.

Available treatment for AMD is limited. For those individuals with well-defined choroidal neovascularization, laser treatment may successfully eradicate the abnormal blood vessels and reduce the chance of further vision loss. Unfortunately, only a minority of individuals with choroidal neovascularization meet the criteria for which laser treatment has been proven beneficial. Conventional laser also damages the retina leaving a blind spot wherever treatment is applied. When new blood vessels invade the space under the center of the macula, treatment with conventional laser results in a scar that affects the central vision. An alternative form of treatment that has been developed is in use at The Retina Center. Photodynamic Therapy (PDT) involves the injection of a medication called Verteporfin (Visudyne) into a vein in the arm which selectively accumulates in the abnormal new vessels. The injection is followed by treatment with a laser that has a wavelength precisely matched to the dye. Damage is usually limited to the abnormal vessels, and scar formation in the macula is limited.

In 2002 the long term results of the AREDS (Age related eye disease study) became available which demonstrated the usefulness of antioxidant vitamin and mineral therapy in preventing severe vision loss from AMD. There are now several commercial preparations of the appropriate dosages of Vitamin C, Vitamin E, Beta Carotene, and Zinc and Copper that should be used only in patients with a specific degree of macular degeneration. Beta Carotene is a building block of Vitamin A and has been reported to enhance the possibility of developing lung cancer in individuals who currently smoke. A modification of this treatment is often made for smokers for this reason. Patients should always consult with their doctor before initiating this type of therapy.

Another worthwhile preventive measure is the use of an Amsler grid. This is a piece of paper with grid lines which an AMD patient can use for self screening. If a new blind spot or area of distortion is noted on the grid, an urgent evaluation is usually indicated.

Some exciting new research gives hope that more effective treatments for AMD may be forthcoming. Most researchers now believe that a genetic influence may be at work in many cases of AMD. That is, many people with AMD may inherit a predisposition for the condition from a parent. Furthermore, there are likely to be a number of different genes that may be capable of causing the condition. Finally, environmental factors such as diet, smoking, light exposure are also likely to play a role but to various degrees depending on the genetic influence. As a result, the future evaluation and treatment of AMD may work something like this:

A 30 year old whose 63 year old mother has AMD wishes to be screened for the disease. While she has a completely normal eye exam, DNA analysis on a blood sample reveals that she does have a known AMD-causing mutation (AMD, type 6) which puts her at a 90% risk for severe visual loss by the age of 65. Biochemical studies have suggested that a diet high in B6 both delays the onset and reduces the severity of this subtype of AMD (other genetic subtypes benefit from other treatments). Smoking has also been shown to be detrimental. She takes B6 daily for the rest of her life, quits smoking, and has regular eye exams. She first develops signs of AMD at age 80 and dies at age 90 with minimal visual difficulties. (PLEASE NOTE: The above example is purely fictional. B6 has not been proven beneficial for any type of AMD and was chosen at random for the purpose of illustration) While the above example will not be possible for a number of years, researchers are already hard at work identifying the genes involved in AMD. In the meantime, individuals with AMD are best served by getting regular dilated eye examinations, performing self-screening with an Amsler grid, taking vitamins as recommended, and not smoking.

Dr. Goldman has extensive experience in the diagnosis and treatment of age-related macular degeneration. If you or someone you know has AMD or other retinal problems, please call to arrange a comprehensive evaluation at either of our convenient locations.

Click here to see photographs of age-related macular degeneration.

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