Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in people beyond age 65 in the United States. It is a slow, progressive, and painless condition that affects the macula, the small central part of the retina that allows you to see fine detail clearly.
While no one knows for sure how many people are affected by AMD, some sources estimate as many as 13 million people in the United States age 40 and older have signs of macular degeneration, and more than 1.2 million have the later, vision-threatening stages of the disease.1
The exact cause of AMD is not yet known, and currently there is no permanent effective treatment or cure for the condition. As the number of older people in the U.S. continues to increase, AMD will become an even greater public health problem in America. This is why research to prevent or delay progression of the condition is so vital.
Scientific and medical research, especially in the area of nutrition and diet, is yielding new information on the role of certain foods in preventing this debilitating condition. And being armed with knowledge about early warning signs of AMD and other ways to protect your eyes, you may be able to keep your vision relatively intact throughout your life.
What is AMD?
AMD occurs when the cells in the macula break down, causing loss of sight in the central part of the field of vision, but leaving peripheral vision intact. Most often, AMD is a slow, progressive, painless disease which often affects both eyes, usually one after the other. Once you are diagnosed with AMD, as many as ten years may pass before you have any noticeable loss of vision. Even though breakdown of macular cells may not begin until age 60 or 70, long–term awareness and preventive measures should begin much earlier in life.
There are two main types of Macular Degeneration:
“Dry” AMD, which accounts for 90 percent of cases, occurs when small yellowish deposits called drusen start to accumulate beneath the macula. These deposits gradually break down the light–sensing cells in the macula, normally causing distorted vision in one eye, then the other. Dry AMD does not usually cause total loss of reading vision. It is important to monitor the progression of dry AMD closely, as it can often progress to the more severe wet form.
“Wet” AMD accounts for the other 10 percent of AMD cases. It occurs when tiny, new, abnormal blood vessels begin to grow behind the retina toward the macula. Here, they often leak blood and fluid that damage the macula, causing rapid and severe vision loss. Wet AMD almost always occurs in people who already have dry AMD, and results in legal blindness in most of its sufferers.
How does AMD affect your vision?
As the cells in the macula deteriorate, your ability to see will begin to change. Objects directly in front of you appear to change shape, size, or color, and may seem to move or disappear. Your vision may become blurry, lines may become distorted, or dark spots may appear in the center of your field of vision. Eventually, AMD results in a circular area of blindness which, at normal reading distance, may block out several words. However, most people with AMD retain a reasonable amount of peripheral vision and can learn to make the most of their remaining vision.
AMD is a highly frustrating condition, which greatly affects your day–to–day living by making it difficult to read, write, drive, and recognize faces. You may also develop problems seeing in bright sunlight or glare, and find it harder to adapt from dark to light conditions.
What are the risk factors for AMD?
Age is the main risk factor for developing AMD. In the United States it is estimated that about 14 percent of people aged 55 to 64 have some form of AMD. This rises to nearly 20 percent of 65 to 75–year–olds, and up to 37 percent of those over 75.2
Diet and Nutrition
The macula’s fragile cells are highly susceptible to damage from oxygen–charged molecules called free radicals. Early research has shown that people with a low dietary intake of antioxidants, nutrients in food that fight the damaging effects of free radicals in the body, may be at increased risk of developing AMD. Alcohol may also deplete the body of antioxidants. High levels of saturated fats and cholesterol harm blood vessels and are also involved in producing free radical reactions that can damage the macula.
The cells of the macula are highly sensitive to sunlight. Cell damage from the sun can lead, over time, to deterioration of the macula. People with light colored eyes may be more prone to damage from sunlight, as are those who have prolonged exposure to ultraviolet light.
A recent study showed that smoking, which reduces protective antioxidants in the eye, more than doubles the risk of AMD.3 The study found that AMD is more than twice as common in people who smoke more than one pack of cigarettes a day, compared with people who do not smoke, and the risk remains high even up to 15 years after quitting.
Some studies show that AMD may be in part inherited. This means that if you have one or more immediate relatives with AMD, you may be at higher risk to develop the condition. If you have relatives who have AMD, you should have your eyes checked.
Gender and Race
Being a women over age 75 doubles your chances of developing AMD compared to a man of the same age. Low levels of estrogen in postmenopausal women may also increase risk for the condition. There is some suggestion that postmenopausal estrogen therapy may be protective of AMD, but more research is needed in that area. Whites are much more likely than African Americans to lose vision from AMD.
If you have high blood pressure or another form of heart disease, you may also have a greater chance of getting AMD because of poor blood circulation to the eyes.
What kinds of tests will my eye care practitioner do to detect AMD?
The tests below should be done at your initial eye evaluation and at each annual exam to insure that any vision loss from wet AMD is found at its earliest possible stages when treatment is more effective. If you are at high risk for developing AMD or have already been diagnosed with AMD, you may need more frequent follow-up exams. Specific tests should always be performed for each eye separately.