The retina is at the back of the eye. It changes light and images that enter the eye into nerve signals that are sent to the brain. A part of the retina called the macula makes vision sharper and more detailed.
AMD is caused by damage to the blood vessels that supply the macula. This change also harms the macula.
There are two types of AMD:
Dry AMD occurs when the blood vessels under the macula become thin and brittle. Small yellow deposits, called drusen, form. Almost all people with macular degeneration start with the dry form.
Wet AMD occurs in only about 10% of people with macular degeneration. New abnormal and very fragile blood vessels grow under the macula. This is called choroidal neovascularization. These vessels leak blood and fluid. This form causes most of the vision loss associated with the condition.
Scientists are not sure what causes AMD. The condition is rare before age 55. It is most often seen in adults 75 years or older.
In addition to heredity, other risk factors are:
You may not have any symptoms at first. As the disease gets worse, you may have problems with your central vision.
SYMPTOMS OF DRY AMD:
The most common symptom in dry AMD is blurred vision. Often objects in the central vision look distorted and dim, and colors look faded. You may have trouble reading print or seeing other details, but you can generally see well enough to walk and perform most routine activities.
As the disease becomes worse, you may need more light to read or perform everyday tasks. A blurred spot in the center of vision gradually gets larger and darker.
In the later stages, you may not be able to recognize faces until they are close.
SYMPTOMS OF WET AMD:
The most common early symptom of wet AMD is that straight lines appear distorted and wavy.
There may be a small dark spot in the center of vision that gets larger over time.
Central vision loss can occur very quickly. If this occurs, you will need urgent evaluation by an ophthalmologist with experience in retinal disease.
Signs and tests
You will have an eye exam. Drops will be placed into your eyes to widen (dilate) your pupils. The eye doctor will use special lenses to view your retina, blood vessels, and optic nerve.
The eye doctor will look for specific changes in the macula and blood vessels. One of the earliest findings in dry AMD are yellow deposits in the macula, called drusen.
You may be asked to cover one eye and look at a pattern of lines called an Amsler grid. If the straight lines appear wavy, it may be a sign of AMD.
If you have advanced or severe dry AMD, no treatment can restore your vision.
If you have early AMD and do not smoke, a combination of certain vitamins, antioxidants, and zinc may prevent the disease from getting worse. But it cannot give you back any vision that is already lost.
The combination is often called the "AREDS" formula. The recommended supplements contain:
500 milligrams of vitamin C
400 international units of beta-carotene
80 milligrams of zinc
2 milligrams of copper
Only take this vitamin combination if your doctor recommends it. Make sure your doctor knows about any other vitamins or supplements you are taking. Smokers should NOT use this treatment.
AREDS may also benefit you if you have a a family history and risk factors for AMD.
The supplements lutein and zeaxanthin may also be helpful, although they are not part of the AREDS formula.
If you have wet AMD, your doctor may recommend:
Laser surgery (laser photocoagulation) -- a small beam of light destroys the leaking, abnormal blood vessels.
Photodynamic therapy -- a light activates a drug that is injected into your body to destroy leaking blood vessels.
Special medications that prevent new blood vessels from forming in the eye (anti-angiogenesis, anti-VEGF therapy) -- drugs such as bevacizumab (Avastin) and ranibizumab (Lucentis) are injected into the eye. This is a painless process.
Low-vision aids (such as special lenses) and therapy can help you use the vision that you have more effectively, and improve your quality of life.
Close follow-up with your eye doctor is important.
For dry AMD, a complete eye exam should be performed by an eye specialist at least once a year.
People who have been treated for wet AMD need frequent, perhaps monthly, follow-up visits.
In AMD, early detection of vision changes is very important. Early detection leads to earlier treatment and often, a better outcome.
The best way to detect changes is by self-testing at home with an eye chart, called an Amsler grid. Test each eye individually with the vision correction you normally wear for reading.
AMD typically does not affect side (peripheral) vision. This is very important, because it means complete vision loss never occurs from this disease. This disorder results in the loss of central vision only.
Mild, dry AMD usually does not cause disabling central vision loss. However, there is no way to predict who will develop a more severe form of the disease.
Wet AMD often leads to significant vision loss.
In general, macular degeneration can cause you to lose the ability to read, drive a car, and recognize faces at a distance. Most people with this eye disease are able to eat, bathe, and perform other regular tasks without too much difficulty.
This condition may make it hard to read, work on the computer, or drive. You may need extra light or magnification to do many of your normal activities.
Calling your health care provider
If you have AMD, your health care provider may recommend that you check your vision every day on an Amsler grid. Call your provider immediately if the lines appear wavy, or you notice any other changes in your vision.
Although there is no known way to prevent macular degeneration, lifestyle factors can reduce your risk of developing the condition:
Eat a healthy diet that is high in fruits and vegetables and low in animal fat
Maintain a healthy weight
See your eye care professional regularly for dilated eye exams.