Macular degeneration: Who's at risk? What can be done?
Age-related macular degeneration is a leading cause of vision loss among older Americans.
Reading, driving, even recognizing a face across the room—these are some of the everyday activities that can be difficult or impossible for someone with age-related macular degeneration (AMD).
AMD affects about 2 million Americans. It's a leading cause of vision loss for older adults, according to the National Eye Institute (NEI).
Experts aren't sure exactly what causes AMD, but it seems to be linked to the body's natural aging process, and age is clearly the most important risk factor, according to the NEI. Other risks factors include smoking and a family history of the disease.
AMD affects a small area in the retina called the macula. The macula is responsible for clear, detailed vision. When the macula breaks down, central vision becomes blurry or distorted.
While central vision is disturbed, peripheral vision remains intact. So even people with severe AMD have some useful vision.
Types of AMD
There are two kinds of AMD: dry and wet. There is no pain with either type.
Dry AMD is by far the most common form. In these cases, the macula slowly becomes thin and breaks down. Vision gradually blurs.
According to the NEI, a common early indicator of dry AMD is the presence of drusen—yellow deposits under the retina often seen by eye care professionals among people over age 60.
On their own, these deposits do not usually affect vision, but as they increase in size and number, AMD risk goes up.
In the earliest stage, dry AMD is often marked by several small drusen or a few medium-sized deposits but no vision loss.
People with intermediate dry AMD have many medium-sized drusen or a few larger deposits. Some central vision may be lost.
Those with advanced dry AMD will have significant drusen as well as a breakdown of cells in the retina's center. An expanding, darkening blurry spot can block central vision.
Wet AMD accounts for about 10% to 30% of cases, but it can be much more serious than the dry form. It occurs when weak, abnormal blood vessels form under the macula. These vessels often leak fluid, which pushes the macula out of place. Vision loss can occur quickly.
There are no stages associated with wet AMD, though many who get this form will have the dry form first.
The most common early sign of wet AMD is that straight lines look crooked. Sometimes, a blind spot blocks central vision.
A complete eye exam can uncover AMD. The exam may include:
- A visual acuity test. An eye chart measures how well you see at various distances.
- A grid test. You look at straight horizontal and vertical lines. If they appear wavy or if some lines are missing, it may point to AMD.
- A dilated eye exam. Drops widen your pupils so that the macula and other structures can be examined with a special magnifying lens.
In addition, if wet AMD is suspected, your eye specialist may suggest a fluorescein angiogram. In this test, a dye is injected in your arm. It travels to blood vessels in the eye, where pictures are taken to spot leaks or other problems.
Since age is a major risk factor for AMD, comprehensive eye exams are important. Your eye doctor can help you set a schedule for your exams.
There is no cure for AMD, but treatment may slow the disease's progress, according to the NEI.
One treatment strategy for wet AMD involves the destruction of leaking blood vessels using either laser surgery or special light-activated drugs. Another method uses drugs to slow the growth of new abnormal blood vessels.
Some treatments for dry AMD may be able to slow its progress, research has shown.
One important study performed by the NEI—called the Age-Related Eye Disease Study (AREDS)—showed that people whose dry AMD had reached the intermediate stage could significantly lower their risk of developing advanced AMD by taking a specific combination of high-dose antioxidant vitamins and zinc.
Unfortunately, the supplements did not seem to help people whose disease was in an earlier stage or to protect people from AMD who didn't already have it.
If you have AMD, ask your doctor if supplements could help save your remaining sight.
Your doctor can also suggest services and devices to help you adapt to lower vision.
To reduce your chances of developing AMD in the first place, the NEI recommends:
- Having a healthy diet high in green, leafy vegetables and fish.
- Maintaining normal weight and blood pressure.
- Exercising regularly.
- Not smoking.