By John Messmer
As people age, many of their bodies' functions change. By 50, most people have experienced the need for reading glasses. The eye's lens stiffens with age so it does not focus as well on close work as in youth. By age 60, many people do not realize they are also at risk for a more serious eye problem --age-related macular degeneration or AMD. The risk increases with age, from about 2 percent at age 60 to about 30 percent over age 75.
At the back of the eyes is a layer of nerves called the retina. Blood vessels beneath the nerves bring oxygen and nutrients to the retina. The retina detects and responds to light, sending electric signals to the brain which organizes the signals into an image. The nerve cells concentrated in an area of the retina, called the macula, register the center of what is observed and respond best to color. If the macula is damaged or deteriorates, the most important part of vision is affected.
While there may be a genetic predisposition to AMD, research has shown that many of the same health problems that lead to heart disease and strokes increase the risk of AMD: smoking, obesity, high blood pressure, lack of exercise and poor diet. Women have a greater risk than men and whites more than African-Americans.
There are two forms of AMD: dry and wet, referring to whether blood vessels behind the retina are leaking. Dry is more common; the typical symptom is blurring in the center of vision, kind of like a smudge in the center of an eyeglass lens. Wet AMD can show up as distortion of straight lines or a blind spot in the center of vision.
Regular eye examinations can detect AMD early. Treatment is available, but results are better if vision has not yet been affected. In wet AMD, newly growing but abnormal blood vessels leak. Treatment involves stopping the leaks and preventing the retina from distorting. Lasers and photodynamic therapy are similar in that they try to destroy the leaky blood vessels. Another treatment is a medication injected into the eye in order to block the growth factors that stimulate new blood vessel growth.
Dry AMD develops more slowly. There is evidence that certain antioxidants can slow its progression. Research is ongoing, and the formulation for antioxidant supplementation will be adjusted as new data are collected. For now, the formulation contains vitamin C, vitamin E, beta carotene, zinc and copper. Dry AMD can develop into the wet form. If dry AMD is found, it's important to follow the supplement recommendations of the treating ophthalmologist. Patients will usually be given an Amsler grid to check their vision daily for distortions, a possible sign of wet AMD developing.
Once AMD is present, high-dose antioxidants are prescribed. While it is not clear whether supplements alone can prevent AMD if it is not present, there are things that may lower the overall risk. Smoking cessation is extremely important, for the eyes as well as the entire body. Proper diet that includes a variety of multicolored fruits and vegetables for the phytonutrients and vitamins they contain; whole grains for their B vitamins and minerals; fish, seeds and nuts for the omega-3 fatty acids; vitamins and minerals which act as antioxidants; and eggs and greens for the pigment lutein which may protect the retina against ultraviolet light. Contrary to what was previously thought, a few eggs per week are acceptable even for people with high cholesterol. A varied diet will provide all the vitamins and minerals needed, except calcium, which might require dairy products or a calcium supplement. Before taking a supplement, seek a doctor's advice since some supplements can be toxic in high doses. Large quantities of these foods are unecessary, because being overweight is another risk for AMD.
Sunglasses with ultraviolet filtration that effectively cover the entire eye, not just the front, will protect the retina. Restrict alcohol use. The safe amount is not clear, but more than one drink daily for a woman or two daily for a man is generally considered excessive. While health benefits from red wine have been noted from many sources, the quantity recommendations still apply.
Regular exercise, 30 minutes a day four or five times a week, can reduce the risk of AMD, heart disease and stroke. It's the single most important contributor to general good health and stamina other than not smoking. Exercise leads to increased levels of nitric oxide in blood vessels, keeping blood flowing smoothly without restriction.
Beginning at age 50, regular eye exams are an important tool to look for early signs of AMD, in addition to glaucoma and other eye problems. With a balanced diet, regular exercise, smoking avoidance, moderation in alcohol use and protection from ultraviolet light, people should greatly increase the chance of clear vision well into old age.
For more information on AMD, go to http://nihseniorhealth.gov/agerelatedmaculardegeneration/toc.html or http://www.nlm.nih.gov/medlineplus/maculardegeneration.html on the Web.
John Messmer is associate professor of family and community medicine at Penn State College of Medicine and a staff physician at Penn State Milton S. Hershey Medical Center.