Macular degeneration - age-related
Macular degeneration is an eye disorder that slowly destroys sharp, central vision. This makes it difficult to see fine details and read.
The disease is most common in people over age 60, which is why it is often called age-related macular degeneration.
Age-related macular degeneration (ARMD); AMD; senile macular degeneration (SMD) is an older name that is no longer in common use.
Causes, incidence, and risk factors
The retina is the inner layer of tissue at the back of the eye. It changes light and images that enter the eye into nerve signals that are sent to the brain. The macula is the part of the retina that makes vision sharper and more detailed.
Macular degeneration is caused by damage to the area around blood vessels that supply the macula. This change in the blood vessels damages the macula.
Two phases of macular degeneration (AMD) exist:
- Dry macular degeneration 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 macular degeneration 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, and is most often seen in adults 75 years or older.
In addition to heredity, other risk factors are:
- Caucasian race
- Cigarette smoking
- High-fat diet
- Female gender
At first you may not have symptoms. As the disease progresses, your central vision may be affected.
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. Straight lines appear distorted and wavy. A blurred or dark 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.
AMD typically does not affect side (peripheral) vision. This is very important, because it means complete vision loss never occurs from this disease.
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 be given drops to enlarge (dilate) your pupils. The eye care provider will then use special lenses to view your retina, blood vessels, and optic nerve.
The doctor will look for specific changes in the macula and blood vessels. One of the earliest findings in dry AMD is drusen, the yellow deposits that form in the macula.
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.
Other tests for macular degeneration may include:
Once dry macular degeneration becomes advanced or severe, no treatment can restore lost vision.
A special combination of vitamins, antioxidants, and zinc may prevent the disease from getting worse if the macular degeneration is not yet severe. It will not bring vision that has been lost, however. This combination is often called the "AREDS" formula.
AREDS may also benefit people with a family history and risk factors for AMD before they have any signs of the disease.
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.
The recommended supplements contain:
- 500 milligrams of vitamin C
- 400 international units of beta-carotene
- 80 milligrams of zinc
- 2 milligrams of copper
Other supplements called 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 the following treatments:
- 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 is important.
- For dry AMD, a complete eye exam should be performed by an eye specialist at least once a year.
- After getting treated for wet AMD, you will 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 Amsler grid. Test each eye individually with the vision correction you normally wear for reading.
AMD Alliance International -- (877) AMD-7171 -- www.amdalliance.org.
Most people with mild dry macular degeneration will not have disabling central vision loss. However, there is no way to predict who will progress to a more severe form of the disease.
The wet form of macular degeneration often leads to significant vision loss.
Although macular degeneration can cause people to lose the ability to read, drive a car, and recognize faces at a distance, it never causes complete blindness. This disorder results in the loss of central vision only -- macular degeneration cannot cause side (peripheral) vision loss.
Nearly everyone with macular degeneration can get around, eat, perform personal hygiene, and do other routine activities without too much difficulty.
Loss of central vision may interfere with many daily activities, such as reading, working on the computer, or driving. You may need extra light or magnification to perform 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:
- Don't smoke
- Eat a healthy diet that is high in fruits and vegetables and low in animal fat
- Exercise regularly
- Maintain a healthy weight
See your eye care professional regularly for dilated eye exams.
Benson WE. Acquired macular disease. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins;2009:chap 23.
Gohel PS, Mandava N, Olson JL, Durairaj VD. Age-related macular degeneration: an update on treatment. Am J Med. 2008;121(4):279-281.
Facts About Age-Related Macular Degeneration. The National Eye Institute (NEI). National Institute of Health. Reviewed September 2009. Accessed July 15, 2010.
Rosenfeld PJ, Martidis A, Tennant MTS. Age-related macular degeneration. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, Mo:Mosby Elsevier;2008:chap 6.27.
Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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