Age-Related Macular Degeneration - KTEN.com - No One Gets You Closer

Age-Related Macular Degeneration

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
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.

Sunlight
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.

Smoking
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.

Heredity
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.

Heart Disease
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.

  • Assessment of your risk of developing AMD based on your family history and lifestyle (such as time spent in the sun, smoking, and diet).
  • Assessment of how you use your eyes at work, at play, and at rest.
  • Nutritional assessment, including information about how, what, and when you eat. If you are at nutritional risk, your eye care professional may recommend a diet rich in certain nutrients to protect your eyes from further damage. Let your specialist know if you have high blood pressure or high cholesterol.
  • Testing of central and peripheral visual fields by looking at a series of lights to detect if any areas of vision are missing.
  • Photos of the retina to establish a baseline to track progression of the disease.
  • Assessment of color vision using a series of circles with numbers.
  • Dilation using special eye drops to make the pupil of the eye larger. This allows the doctor to use a light and a large lens to evaluate the condition of the entire retina, especially the macula.
  • Testing of your visual sharpness at far and near distances and a detailed evaluation of how words look on a page when reading.
  • Visual functioning status to assess how each eye works separately and how both eyes work together to see far and near objects. Your mobility can also be assessed to determine your risk for potential problems if AMD affects your ability to walk and drive.
  • Amsler grid testing to evaluate any distortions or abnormalities in vision. This is the easiest way for you to monitor yourself at home.
What help is available for people with AMD?
While there have been a few new inroads built for the treatment of AMD, the FDA has approved a treatment that uses a photo-reactive dye with a non-thermal laser to seal the leakage from abnormal blood vessels in the retina. The drug is injected into a vein in the arm of the patient. After 20 minutes, allowing the drug to target the leaking blood vessels, a special laser that does not produce any heat is focused into the area to be treated. The laser causes the drug to react, which effectively closes off the leaky vessels. This breakthrough treatment, known as photodynamic therapy, causes no scarring of the retinal tissue, which has been a side-effect of the current laser therapy.

Photodynamic therapy does not reverse damage, or cure AMD, but in some cases it can significantly slow the progression, allowing patients additional years of sight. Photodynamic therapy is not effective for every patient with AMD. Patients should consult with their doctor to determine if they would benefit from treatment.

For those with severe AMD, low-vision aids such as magnifying devices, large-print reading materials, or closed-circuit televisions and computers can be used to assist with reading and driving. Eye care practitioners trained in behavioral and functional therapy can plan a vision therapy program to help you maintain reaction times and continue to read and remain mobile.

While there currently is no cure for AMD, promising research is being done in a wide variety of areas, including radiation, nutritional, drug, and surgical therapies. We must continue to look for ways to prevent or delay the progression of this condition, so that future generations of older Americans will not be disabled by macular degeneration.

1. Prevent Blindness America. Vision Problems in the U.S. Schaumburg, IL, 1994.
2. Klein R, Klein B, Linton KLP. Prevalence of age-related maculopathy. The Beaver Dam Eye Study. Ophthalmology. 1992; 99:933-43.
3. West, S.K., 1999, Smoking and the risk of eye diseases in "Nutritional and Environmental Influences on the Eye." Taylor, A., Editor, CRC Press, Boca Raton, FL, pp. 151-164.