Age-related macular degeneration (AMD or ARMD) is the leading cause of irreversible vision loss in people older than 60.
What it is
Macular degeneration is a chronic, progressive, and painless condition that causes the death of cells in the macula, the small central part of the retina that allows you to see fine detail. It blurs the sharp, central vision needed for activities that require straight-ahead vision, such as reading, sewing, and driving.
There are two types of AMD: wet and dry. Both destroy central vision. Color vision and distance vision also are affected.
Dry AMD, which accounts for the majority of cases of AMD, occurs when cells in the macula begin dying for no apparent reason. The damage causes gradual blurring of the central vision in the affected eye. Often, only one eye is initially affected; later, the second eye may become involved. The most common symptoms of dry AMD are slightly blurred vision, difficulty recognizing faces, or needing more light for reading. The dry form also can turn suddenly into the wet form; there is no way to tell if or when the dry form will turn into the wet form. Dry AMD usually does not affect peripheral (side) vision.
Wet AMD is more serious than dry AMD and affects about 10 percent of all cases. It occurs when new blood vessels behind the retina start to grow under the macula. New blood vessels are fragile and often leak fluids under the macula. The blood and fluid raise the macula from its normal place at the back of the eye. This damages the macula, causing rapid and significant vision loss. An early symptom of wet AMD is straight lines that appear wavy. Peripheral vision, normally preserved in the dry form of AMD, may be seriously affected in the wet form. Therefore, wet AMD is more likely to lead to total blindness.
See your doctor if you notice any of these symptoms:
A sudden or gradual loss of ability to see clearly, such as difficulty reading fine print or needing more light for reading or doing close work
A decrease in ability to identify colors
Distorted vision, such as wavy lines that should be straight
A dark or empty spot appearing in or near the center of vision
Blurry or fuzzy vision
Difficulty seeing at a distance
Causes and prevention
AMD is most common among people older than 50, but the American Academy of Ophthalmology says it can appear as early as age 40. These factors increase the risk for AMD:
Advancing age. Individuals over age 75 have a 30 percent chance of developing AMD.
Obesity. Research suggests a link between obesity and the progression of early and intermediate stage AMD to advanced AMD.
Race. Whites are much more likely to lose vision from AMD than are African-Americans.
Family history. People with a family history of AMD are at higher risk for developing the disease. In some people, AMD may be associated with an immune system response caused by an inherited gene. Genes have been located that are thought to account for about 25 percent of the cases of AMD.
Gender. Women appear to be at greater risk than men for AMD.
High blood pressure and other forms of cardiovascular disease
AMD may be brought on or worsened by dietary deficiencies, high blood pressure, smoking, and exposure to high levels of ultraviolet (UV) light and blue light.
These steps may help delay the onset of AMD or slow its progression:
Eat five to nine servings a day of fruits and vegetables, especially those rich in vitamins A, C, and E.
Take a vitamin supplement containing antioxidants, zinc, copper, and lutein. Ask your eye care professional which supplement you should take.
If you smoke, quit. Multiple studies have linked smoking to AMD.
Eat a low-fat diet. High levels of saturated fat and cholesterol harm blood vessels and produce free radicals that can damage the macula.
Wear sunglasses that block 99 to 100 percent of UV radiation and screen out blue light.
Manage high blood pressure. This condition can reduce blood circulation to the eyes.
Exercise regularly. Keeping physically active improves blood circulation to the eyes.
Get regular eye exams. How frequently you should have an eye exam depends on your age and the other risk factors you have for AMD. Your health care provider can help you decide how frequently you should have exams.
AMD can only be diagnosed with a comprehensive eye exam. This exam should be done by a qualified eye care professional and should include these tests:
Visual acuity test. This uses a standard eye chart with letters of various sizes to test how well you see at various distances.
Dilated eye exam. In this exam, drops are used to dilate the pupils, and the doctor examines your retina and optic nerve. A common sign of AMD are yellow deposits under the retina called drusen. These deposits can be found during a dilated eye exam.
You may be asked to look at an Amsler grid, which looks like a checkerboard. This grid is used to test for AMD. You look at a black dot in the center of the grid with one eye covered, and repeat with the other eye. If you notice that the straight lines in the pattern appear wavy or appear to be missing while staring at the dot, you may have AMD.
There is no cure for AMD. Treatment attempts to halt the progression of AMD.
High doses of certain vitamins may slow or halt the vision loss caused by AMD. The Age-Related Eye Disease Study in 2001 indicated that people with moderate to advanced wet or dry AMD reduced their risk for further vision loss by taking high doses of zinc, beta carotene, and vitamins C and E. The supplement combination tested was a daily dose of 500 mg of vitamin C, 400 IU of vitamin E, 15 mg of beta carotene (often as vitamin A; up to 25,000 IU), 80 mg of zinc (as zinc oxide), and 2 mg of copper (as cupric oxide). Talk to your healthcare provider before taking these supplements, because there may be health risks. If you are a smoker or a former smoker, high doses of beta carotene (vitamin A) may increase your risk for lung cancer. Doses of vitamin E higher than 400 IU have been associated with an increased risk for cardiovascular death. Lutein has been shown to slow down the progression of AMD and while the daily amount is still under investigation, most eye doctors advise taking 10 to 20 mg per day.
No treatment is currently available to reverse the process of dry AMD. Researchers are looking at photocoagulation as a possible way to delay vision loss. Your eye care provider might recommend taking high doses of zinc, beta carotene, and vitamins C and E to prevent progression of AMD.
Damage from wet AMD usually cannot be reversed, but further damage can be prevented with treatment. For some types of wet AMD, a high-energy laser beam can be used to destroy the new abnormal blood vessels. This therapy is called photocoagulation. For other types of AMD, a cold laser combined with a light-sensitizing drug called verteporfin can be used to close new abnormal blood vessels. This is called photodynamic therapy. Surgery is another treatment option for some types of wet AMD.
Two drugs have been approved by the FDA to slow or block the growth of new blood vessels, thus preserving sight. Both are injected into the eye. Pegaptanib is a drug that is injected every six weeks; ranibizumab is injected monthly.
Another drug, bevacizumab, originally approved to treat colorectal cancer, has shown in a preliminary study to reduce leakage from abnormal blood vessels in the retina. Many other drugs are being studied.
Living with AMD
People whose vision has been damaged by AMD can be helped by low vision specialists with the use of magnifiers and nonoptical aids, such as large print books. Ask your eye doctor about these options and the availability of low vision clinics in your area. Most people can be helped to lead a comfortable lifestyle.
If you have dry AMD, the National Eye Institute (NEI) recommends that you have a comprehensive eye exam at least once a year and ask your eye care provider if high dose supplements would help delay the advancement of the condition.
Because dry AMD can turn into wet AMD at any time, the NEI recommends you get an Amsler grid from your eye care professional and use it every day to test your vision for signs of wet AMD. This is how NEI recommends you use the Amsler grid: Check each eye separately; cover one eye and look at the grid, then cover your other eye and look at the grid. If you detect any changes in the appearance of this grid or in your everyday vision, call your eye care provider.
If you have wet AMD and your doctor advises treatment, the NEI advises that you do not wait. After treatment, you should have frequent eye exams to detect any recurrence of leaking blood vessels. In addition, check your vision at home with the Amsler grid. If you detect any changes, schedule an eye exam immediately.