Age Related Macular Degeneration (abbreviated AMD) is the leading cause of blindness in Americans over 65. The disease occurs in the light sensitive layers that form the back of the eye—the retina and the choroid. AMD affects the central vision and causes the targets in the center to look distorted, blurry, or absent. This distorted vision creates a major health problem for older adults and has significant impact on functional status and quality of life. Visual impairment limits the ability to read or to safely drive a car and is associated with increased rates for falls and hip fractures. AMD is estimated to affect more than 8 million individuals in the USA. The disease is more common in people as they age: so as Americans continue to live longer, AMD will become more prevalent and a greater health hazard.
The disease is classified into two forms: “Wet” or neovascular AMD in which abnormal circulation develops underneath or within the retina, and “Dry” or atrophic AMD in which vision is lost to an accumulation of metabolic waste product underneath the retina. Atrophic AMD makes up 85-90% of the cases, with neovascular AMD constituting 10-15%. . The disease commonly affects both eyes, albeit with a variable severity in each eye. In some cases, previously dry AMD may progress to the wet type.
AMD is diagnosed by a doctor specializing in eye disease. Many patients will have symptoms suggestive of the disease, like distorted or wavy central vision. These patients should seek medical attention urgently. However, some patients can be diagnosed before they have any symptoms. To facilitate early diagnosis of eye disease, the American Academy of Ophthalmology recommends a comprehensive eye examination for all adults, with a first exam at age 40 for individuals without a family history of eye disease. Individuals with vision problems or with a family history of eye disease should see a doctor sooner.
The doctor will perform a full exam of the eyes, which includes a dilated exam to assess the retina. Individuals with AMD have abnormal findings in their retina in a central area known as the macula. Drusen, or yellow deposits, are the hallmark finding in atrophic AMD and may be associated with darker spots as the Retinal Pigment Epithelium becomes involved. Patients with wet AMD will have bleeding or swelling in their retina.
Early, dry AMD may be managed by a comprehensive Eye care provider, while more advanced cases are usually referred to an Ophthalmologist who specializes in care for retinal diseases. In an initial exam, a retina specialist will perform different specialized tests to classify the AMD. These tests may include photographs, angiography of the retina or a scan to seach for subtle swelling in the macula. All tests, and most treatments, can be performed in the office.
Prevention and Treatment
The last decade has brought major breakthroughs in the prevention and treatment of AMD. Prevention of vision loss is vital in dry AMD as there is currently no therapy that can restore vision once lost. The National Institute of Health (NIH) completed a trial called the Age Related Eye Disease Study which established vitamin therapy as the cornerstone for treatment for AMD. Individuals with early AMD can have a 25% reduction in their risk of progressive disease overt five years if they are treated with a blend of anti-oxidants and minerals—vitamin C 500 mg, vitamin E 400 IU, beta-carotene 15 mg, zinc oxide 80 mg and cupric oxide 2 mg. This mix of vitamins is sold under multiple names including Preservision and I-Caps. The vitamin blend was not shown to be useful for people without AMD or for individuals who already had advanced disease in both eyes. Smokers were shown to have an increased risk of lung cancer with beta-carotene treatment, so a version of the formula without beta-carotene is also available. Quitting smoking is the most beneficial choice that a smoker at risk for AMD can make.
The NIH is currently completing a follow up trial to assess the benefit of additional nutrients-- lutein, zeaxanthin, and omega-3 fatty acids. The final results from that trial are expected in 2013. Studies of diet have suggested that most patients would benefit from eating fatty fish at least twice a week: Salmon, Anchovies, Bluefin tuna, Herring, Macrel, Sardines, or Trout are all good choices. Additional, leafy, green vegetables contain protective nutrients: kale, spinach, chard and collard or turnip greens are especially high in lutein.
Currently, Wet AMD has multiple treatments that can either prevent ongoing loss of vision or restore vision that has been lost to macular exudation. The typical treatment consists of a series of injections of medication into the eye. The injections are given once monthly at the onset of treatment, but the interval between treatments may be extended once the disease has responded. There are four different injections available ( Macugen, Lucentis, Avastin, and Eylea) and the choice of agent is tailored to the particular patient. Other treatments for wet AMD include thermal laser photocoagulation and Photodynamic Therapy.
AMD is a critical health problem effecting Americans as they age. Fortunately, many advances have been made in the care of patients with AMD. Avoiding tobacco and eating a diet rich in fish and vegetables is the best primary prevention strategy. Early diagnosis and early treatment after the onset of disease can prevent loss of vision. Preservation of vision averts the loss of independence and function that many American seniors once had to endure.
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