Age-related macular degeneration (AMD), an eye disease associated with aging, gradually destroys the sharp, central vision that is needed for seeing objects clearly and for such common daily tasks as reading and driving. It’s the leading cause of vision loss in Americans 60 and over.
In some cases, AMD advances so slowly that people notice little change in their vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. Affecting the part of the eye called the macula, which is located in the center of the retina, AMD is not accompanied by pain.
The greatest risk factor for AMD is age. Other risk factors include smoking, obesity, race (African Americans have the greatest likelihood), gender (women more than men) and family history. Although it may occur during middle age, it affects most people over age 60, with a risk of about 30 percent for those over 75.
There are two types of age-related macular degeneration – wet and dry. Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula. These new blood vessels, which tend to be very fragile, often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye and incur damage. Loss of vision can occur quickly. An early symptom is that straight lines appear wavy.
Dry AMD occurs when the light-sensitive cells in the macula slowly break down, gradually blurring central vision in the affected eye. As the condition grows worse, it often causes a blurred spot in the center of one’s vision. Over time, as less of the macula functions, central vision is gradually lost. With the dry condition, you may have difficulty recognizing faces and may need more light for reading and other tasks. While it generally affects both eyes, vision can be lost in one eye while the other eye seems unaffected.
Wet age-related macular degeneration is typically treated with laser surgery, photodynamic therapy, or injections into the eye. None of these is a cure. In laser surgery, the fragile, leaky blood vessels are destroyed by aiming a high energy beam of light directly at them to prevent further loss of vision. However, laser treatment may also destroy some surrounding healthy tissue and some vision. The risk of new blood vessels developing after laser treatment is high. Repeated treatments may be necessary and, in some cases, vision loss may progress despite repeated treatments.
In the case of photodynamic therapy, a drug called verteporfin is injected into the arm. It travels throughout the body, including the new blood vessels in the eye. The drug “sticks” to the surface of new blood vessels. A light is then shined into the eye for about 90 seconds, activating the drug. This destroys the new blood vessels and leads to a slower rate of vision decline. Unlike laser surgery, this drug does not destroy surrounding healthy tissue. The therapy is relatively painless.
Wet AMD is also treated with new drugs that are injected into the eye (anti-VEGF therapy). Abnormally high levels of a specific growth factor occur in eyes with wet AMD and promote the growth of abnormal new blood vessels. This drug treatment blocks the effects of a growth factor that promotes the growth of abnormal blood vessels. This treatment, which involves the need for multiple injections, can help slow down vision loss and in some cases improve sight.
In the case of dry AMD, once it reaches the advanced stage there is no form of treatment available to prevent vision loss. However, treatment can delay and possibly prevent intermediate AMD from progressing to this stage. This involves the use of a specific high-dose formulation of antioxidants and zinc.