WHAT IS AGE-RELATED MACULAR DEGENERATION (AMD)
Age-related macular degeneration (AMD) is a common, serious disease of the eye’s retina. This condition is associated with aging and gradually destroys the sharp, central vision that is needed for seeing objects clearly and for common daily tasks such as reading and driving. The disease progresses faster in some people than in others and may lead to a loss of vision in one or both eyes. AMD is the leading cause of legal blindness in the United States.
The retina is the paper-thin tissue that lines the back of the eye and sends visual signals to the brain. In the center of the retina is a small area (about one-fifth of an inch in diameter) called the macula. It is made up of millions of closely packed, light-sensing cells that produce your central vision. In AMD, there is a slow breakdown of the cells in and behind the macula, accompanied by a gradual loss of central vision.
Late-stage AMD occurs in two forms—dry (or atrophic) and wet (or exudative). The dry type basic cause is not yet known and is a topic of much scientific investigation. As AMD worsens, new blood vessels may begin to grow. Because these new vessels tend to be very fragile, they will often leak blood and fluid under the macula, resulting in wet AMD. This can cause rapid damage to the macula that can lead to the loss of central vision.
WHO IS AT RISK FOR AMD?
The greatest risk factor is older age; people over age 60 are at a much greater risk than other age groups; although the chance of having AMD is only 1 percent at age 55-64, this prevalence rises to 4 percent for those over 65, and 30 percent of the population over age 75.
Because women live, on average, several years longer than men, women are twice as likely as men to develop the condition. The lifetime risk for getting AMD is 6 percent for females and 3 percent for males.
Therefore, women need to be more aware of AMD, and older women should be sure to visit an eye care professional at least every other year. After increasing age, smoking is the strongest predictor of who will get AMD; this habit can double the risk of the disease. Family history is also important; people whose immediate family members (including grandparents) had AMD are at higher risk of developing the disease. Scientists have found numerous genes are responsible for this hereditary component, although other non-genetic factors can also be familial.
WHAT ARE THE SIGNS AND SYMPTOMS OF AMD?
The early signs of susceptibility to AMD are deposits behind the retina called drusen. These are visible to the ophthalmologist or optometrist examining your eyes. Most older people have some small, “hard” drusen, which are not a cause for concern. However, large, “soft” are risk factors for progression to more advanced, symptomatic AMD. Neither dry nor wet AMD causes any pain.
The most common early symptom of dry AMD is blurred central vision, even when glasses or contact lenses are being worn. When fewer cells in the macula are able to function, patients will see details in front of them, such as faces or words in a book, less clearly. Often this blurry spot will, at first, go away in brighter light. But if the loss of the central, light-sensing cells becomes great, people may see a constant small and growing, dark, or empty area in the middle of their field of vision.
Another classic early symptom of wet AMD is that straight lines appear curved or distorted. This results when fluid from the leaking blood vessels gathers and lifts the macula, distorting vision. Eye care providers may suspect AMD if a patient is over age 60 and has had recent changes in his or her central vision. To look for signs of the disease, the doctor will use eye drops to dilate, or enlarge, the pupils, allowing a clear view of the back of the eye. The patient may also be asked to view an Amsler grid, a pattern that looks like a checkerboard. Changes in central vision will cause the grid to appear distorted or some of the grid will be dark. These are some signs of AMD.
As the loss of central vision progresses, the decrease in the ability to drive, read, and see faces can result in loss of independence. Because of poor eyesight, there is an increased risk of falling, which can result in hip fractures, especially in women, since osteoporosis is much more common in women than men.
WHAT CAN BE DONE TO HELP PREVENT OR LIMIT AMD?
There is no way to prevent getting older or to change your genes. However, you can protect yourself in other ways. Most importantly, this is one more reason to stop smoking. Another important lifestyle factor is your diet. There is strong evidence that a diet rich in fruits and dark green vegetables lowers the risk of AMD. Specifically, nutrients called carotenoids such as lutein and zeaxanthin which are found in dark green leafy vegetables and other foods are protective. There are many other compounds in food which are important for prevention, like the fats in fish, so the best advice is to eat a healthy diet. One study showed that a diet supplemented with an antioxidant combination (vitamins C and E, carotenoids, , and zinc with copper) slowed the progression in some people who already have moderate AMD; however, these food supplements appeared to have no effect in preventing the disease in otherwise healthy individuals. Other healthy habits that are related to AMD include maintaining a healthy weight and exercise.
Bright light may be involved in the process that starts AMD, so it is prudent for you and your children to wear hats and sunglasses to protect your eyes in bright sunlight. Because of the genetic component to AMD, if a close relative had the disease, there is more reason to monitor your vision closely and to have frequent eye examinations. It is recommended that everyone over age 60 be examined at least every two years by an eye care professional. One reason is to detect AMD early, as there is no pain or other symptoms in early stages. In this way, the disease can be followed and arrested before a harmful retinal hemorrhage occurs.
If you already have wet AMD in one eye, you are at higher risk of having your other eye progress to the late stages. You need to see your eye-care professional often and check an Amsler grid at home.
WHAT TREATMENT IS AVAILABLE FOR AMD?
Unfortunately, no effective treatment now exists for the dry form of AMD. However, it is crucial that patients who progress to wet AMD and need treatment have it done before the disease destroys their central vision. For this reason, if you have early AMD, you should have your eyes examined through dilated pupils at least once a year.
The main treatment for wet AMD uses antibodies to inhibit a growth factor (VEGF) that is largely responsible for forming the new blood vessels. This treatment can slowthe progression of the vessels, and may improve vision in some cases. The drugs (typically Eylea, Lucentis or Avastin and newer treatments) need to be injected monthly directly into the vitreous jelly of the ailing eye. The rate of serious complications is very low.
Research in molecular biology, genetics, and epidemiology has shown that inflammatory processes may trigger AMD; learning more about this aspect of the disease may lead to novel treatments in the future.
It’s been estimated that three-quarters of blindness and vision loss is preventable or treatable. There are several lifestyle choices you can make to reduce the risk of getting eye diseases.
You can optimize your eye health by practicing a healthy lifestyle, having regular eye exams, and protecting your eyes from injury.