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Macular Degeneration
Deterioration of the part of the eye called the macula causes a loss of the central part of your visual field ("central vision"). Central vision, normally your sharpest, most useful vision, may become so impaired that things you look at directly may seem blotted out, smudged, or shrouded in a dark haze.
Because the condition tends to appear later in life, it is also called age-related macular degeneration, or AMD. AMD is the leading cause of poor vision in people over 60, though it can also occur at younger ages. Fortunately, peripheral vision remains normal, so even severe macular degeneration does not lead to total blindness. You will still be able to see off to the sides.
What Is the Macula?
The macula is the centermost part of the retina, the light-sensitive membrane of nerve tissue that lines the back of the eye. The retina is the "screen" upon which images are focused by the optical parts of the eye (cornea and lens). Although it's no larger than a pinhead, the macula contains the visual cells needed for sharp vision and for seeing straight ahead. If those cells are damaged, it becomes difficult or impossible to see fine detail and read small print.
What Causes AMD?
Scientists have not yet learned why a macula that has functioned normally for many decades begins to degenerate. Heredity is likely to play a role. Long-term exposure to bright sunlight may be involved. It is also possible that tissue changes that normally accompany aging somehow interfere with the macula's getting enough oxygen and nourishment.
Recent studies have found a higher risk of AMD among smokers and former smokers. Other studies have found a relationship between a high intake of saturated fat and AMD. People who develop AMD are typically in good health. The condition does not appear to be caused by arteriosclerosis, high blood pressure or diabetes, or by drinking alcoholic beverages. It is not caused by using your eyes too much.
Types of AMD
There are two major types of AMD, called dry and wet. Most patients have the dry type, which tends to develop slowly as the tissue beneath the macula gradually deteriorates. The wet type occurs when these tissue changes are accompanied by the formation of tiny abnormal blood vessels under the retina, called subretinal neovascular membranes, and these start to leak fluid or bleed. The lost visual sharpness is caused by fluid that has leaked under the macula and lifted it out of position. With either type, small deposits called drusen may build up under the macula. Though drusen may be a normal and harmless sign of getting older, they also may be a sign that degenerative macular changes are starting to develop.
Symptoms
The typical first symptom (either type) is a blurring of vision in one or both eyes. When the blurring is gradual, you may think you need new eyeglasses. But a new prescription is not likely to improve your vision because the problem is not with the optical parts of the eye.
As time goes on, you may notice a hazy or dark zone in the center of objects you look at directly. And colors may begin to look different or lose richness. With the wet type especially, vision may become distorted and "wavy," so that straight lines, such as the edges of doors and windows, look bent or crooked. Any of the symptoms may be gradual or sudden, but the more abrupt changes are more likely to occur with the wet type.
Examination
Your vision will be checked and you will have a refraction (test for glasses) along with a complete eye exam. Your pupils will be dilated (enlarged) with eye drops so that the inside of the eyes can be evaluated with an ophthalmoscope. A special type of observation lens or contact lens may be used on each eye to allow the retina and macula to be examined under high magnification with a slit-lamp microscope.
Photographs may be taken of your retina. Pictures are useful in determining the extent of the problem and in evaluating its progression. If you have a test called fluorescein angiography, an orange-colored dye will be injected into a vein in your arm and a rapid series of retinal photographs taken as the dye travels through the eye's blood vessels. By identifying the position and extent of any abnormal blood vessels and any leakages, the angiogram provides important guidance for treatment.
Treatment
Dietary suplements: So far, there are no medications for treating Dry AMD. Dietary supplements (antioxidants, vitamins and minerals) have been suggested as a way to slow the degeneration, but scientific evidence for their effectiveness is inconclusive. Some studies show beneficial results, other don't. Long-term research is being conducted to help clarify whether supplements are effective. In the meantime, it seems prudent to take a regular vitamin-mineral supplement for whatever potential help it might offer. (The cost, however is not inconsequential.)
Laser surgery: Sometimes, in the early stages of the wet type of AMD, a laser can be used to seal the leaks or to destroy the abnormal blood vessels under the macula. (Laser surgery does not help the dry type.) What is hoped for is that laser treatment will help stabilize or even improve vision. But please don't expect miracles. There are also newer medications that are given by injection that are very helpful in Wet AMD.
The use of a laser involves some risk because a laser can destroy normal neighboring tissue as well as abnormal tissue. So the surgery will be recommended only if the risk is small and there is a reasonable chance for success. It will not be attempted if the degeneration is too extensive, too advanced, or in too critical a location. Laser surgery seems to be most helpful and least risky when the angiogram shows leaks that are not too near the center of the macula.
What to Expect
AMD usually comes on gradually or in small spurts over many months and then its progress slows down or stops. Eventually, both eyes are likely to be affected, though the degeneration in one eye may precede the other, sometimes by years. There is also the possibility that new "wet" changes will occur later, even after successful treatment, or they can develop in someone who originally had the dry type. Sometimes the degenerative process stops before vision is reduced very much. Unfortunately, that does not happen often enough. In most cases, vision continues to decrease to the point that reading is hampered, and driving a car is no longer safe.
If vision in both eyes drops to a level that cannot be improved with eyeglasses to better than 20/200 (the "big E" on the eye chart), the term "legal blindness" is used. But do not be frightened. This is merely a legal definition used for determining eligibility for certain social services (and an extra income tax exemption). Remember, even if the degeneration is severe, side vision will remain normal. You should continue to see well enough to move about comfortably and care for yourself. Some patients even surprise everyone by being able to see and pick up small objects from the floor.
What You Can Do
In addition to having regular eye exams, you should take a few seconds every day to check your vision with an Amsler grid, a small card printed with a pattern of crossing straight lines that form squares. The lines should look straight and solid. If any of them start looking wavy or having missing segments - which could indicate the beginning of wet changes that might be treatable - you should have your eyes examined within the next few days. It is frightening to face the prospect of losing central vision. But you can learn new ways to use the sight you have to best advantage. Most people quickly learn how to use their peripheral vision more effectively, which includes learning to look slightly off-center.
A low vision specialist can be a great help. This professional can work with you to select special eyeglasses and magnification devices that could allow you to see better in certain situations. He or she will also introduce you to non-optical aids, such as large-type books and magazines, large press-on numbers for your appliances, and even talking clocks. Consider joining a support group. You may find it comforting to talk to others who share similar problems and exchange helpful ideas with them . If your problem seems especially overwhelming, you may wish to seek professional psychological support.
Always keep in mind that using your eyes will never harm them. You can continue any of your usual activities as long as they feel comfortable to you. Even with reduced vision, your life can be surprisingly normal and fulfilling.
Macular Degeneration
