By: Frere Gremillion, MD, for SENIOR Magazine (Northshore Edition)
Age-related macular degeneration (AMD) is the leading cause of blindness for those age 55 and older in the United States, affecting more than 10 million Americans. This disease is caused by the deterioration of the central portion of the retina, called the macula. The macula is responsible for focusing central vision in the eye, and it controls our ability to read, drive a car, recognize faces or colors, and see objects in fine detail.
When AMD occurs, those affected notice difficulties with their central vision. The words on a page may appear blurred or straight lines may look distorted or crooked. Peripheral vision is not affected in AMD, therefore total blindness does not occur in this disease. Loss of central vision can impair individuals in performing most activities of daily living and can make it difficult for people to live independently.
There are two forms of macular degeneration: dry and wet. Dry macular degeneration is the more common form of the disease and accounts for 90% of all AMD. Small yellowish deposits called drusen lead to the development of dry macular degeneration. Drusen, which are composed of proteins, lipids, and other elements, accumulate under the retina and eventually may result in atrophy or deterioration of the overlying normal retina. These areas of atrophy may become large enough to affect the central vision, sometimes quite severely.
Wet macular degeneration is less common, but more severe than the dry form. It accounts for approximately 10% of all AMD, but 90% of all blindness from the disease. This form is characterized by the growth of abnormal blood vessels beneath the retina, which is known as choroidal neovascularization. These vessels have a tendency to bleed or leak fluid under the macula and cause a drop of visual acuity. If left untreated, the wet form may rapidly cause permanent loss of central vision.
There are multiple risk factors for AMD. The first and most important risk factor is age. Approximately 10% of patients 66 to 74 years of age will have findings of macular degeneration. The prevalence increases to 30% in patients 75 to 85 years of age. Smoking is the most established modifiable risk factor for AMD. Several studies have established an association between smoking and macular degeneration. Smokers have a two to three fold higher risk of developing AMD than patients who have never smoked. There is also evidence that the likelihood of developing AMD would be reduced if one were to quit smoking. Current or ex-smokers cannot take the vitamin supplements that have beta-carotene because it increased the risk of developing lung cancer.
AMD also appears to be hereditary in some families. If a patient has a first-degree relative with AMD, that greatly increases the likelihood of that patient developing AMD. A patient that does not have any relatives with AMD has a much lower chance of developing the condition.
Currently there is no effective treatment for dry AMD. A large-scale study showed that people who have dry AMD could benefit from taking certain antioxidants. The purpose of taking these antioxidants is to slow the progression of the disease, not to reverse any damage that has already occurred. Vitamin A (beta-carotene), Vitamins C and E, and well as Zinc were the main nutrients that showed benefit in patients. It has also been suggested that lutein and zeaxanthin may also slow the progression of AMD.
Wet AMD can be effectively treated if treatment occurs early on in the disease. There are two effective agents, known as vascular endothelial growth factor inhibitors, (VEGF) which have showed excellent clinical results in treating wet AMD. These VEGF inhibitors not only can stabilize wet AMD but may also improve visual acuity in a large number of patients. However, many patients may have both a combination of wet and dry AMD, which makes the overall prognosis guarded in maintaining visual acuity.
It is highly recommended for any person over the age of 60 to have his or her eyes checked for the presence of AMD. For smokers or patients with a family history of AMD, they should be checked at an earlier age. Early detection and initiation of antioxidant therapy is important is reducing the chance of severe vision loss from this disease.
Frere Gremillion, MD is the Vitreoretinal Specialist at the Vitreoretinal Eye Center. He may be reached a 985-867-9100.