Age-related macular degeneration
Key points
- Macular degeneration is a common cause of blindness and vision impairment among people older than 50 in the United States.
- Dry AMD sometimes does not cause any symptoms, or it can cause minimal loss of central vision clarity.
- Your doctor will ask questions about your health history and about any risk factors you might have for AMD.
- However, only a small fraction of people with early nonneovascular AMD do not develop advanced AMD with vision loss.
What Is It?
Macular degeneration is a common cause of blindness and vision impairment among people older than 50 in the United States. This condition also is called age-related macular degeneration, or AMD. AMD damages the macula, a small part of the eye's light-sensitive retina, the layer of tissue that sends vision signals to the brain. Because the macula is responsible for seeing sharp details directly in the center of the field of vision, damage caused by AMD can interfere with:
- The ability to see straight ahead, necessary for driving and viewing distances, such as when recognizing faces or watching television
- Fine, detailed vision, necessary for reading newsprint, sewing, working with crafts and making repairs
Macular degeneration is characterized by deposits known as drusen that develop in the macula, although the reason these deposits accumulate is not known. There are two ways to lose vision as a result of macular degeneration. Both occur during the early stage of the disorder.
- Dry (nonneovascular) AMD — About 90 percent of people who lose significant vision from AMD have this form of the illness. In dry AMD, the layer of cells under the retina stops functioning well, causing the light-sensing cells that overlie drusen to dysfunction or disappear over time, producing subtle and, later on, overt blank spots in an eye's central vision.
- Wet (neovascular) AMD — In wet AMD, delicate new blood vessels begin to grow beneath the retina and can leak blood and fluid into the macula, causing scarring. Damage from the blood vessels, blood and fluid, and scar tissue can occur in a very short period of time, causing rapid loss of vision over days to weeks and continued loss of vision over time. This aspect of the disease is probably responsible for about 90 percent of the cases in which AMD has led to legal blindness.
Age is the most important risk factor for AMD, and the early stage (drusen) currently affects approximately 3.5 million to 10 million people in the United States older than 65. The exact number depends on how drusen is defined. Only a small percentage of people in their 50s have AMD. This percentage increases dramatically in people aged 75 and older. In that age group, about 10 percent have the advanced form of AMD that causes vision loss. AMD also may be slightly more common in women and in those with a family history of AMD. Caucasians may be at greater risk of developing the wet form. Cigarette smoking and risk factors for cardiovascular disease, such as high levels of blood cholesterol, may be additional risk factors for AMD.
Symptoms
Dry AMD sometimes does not cause any symptoms, or it can cause minimal loss of central vision clarity. In a small number of cases, it gradually advances to cause more significant blurring in the center of the field of vision. In these more advanced cases, faces and printed words become hard to recognize.
Frequently asked questions
What is age-related macular degeneration?
Macular degeneration is a common cause of blindness and vision impairment among people older than 50 in the United States. This condition also is called age-related macular degeneration, or AMD. AMD damages the macula, a small part of the eye's light-sensitive retina, the layer of tissue that sends vision signals to the brain.
What are the symptoms of age-related macular degeneration?
Dry AMD sometimes does not cause any symptoms, or it can cause minimal loss of central vision clarity. In a small number of cases, it gradually advances to cause more significant blurring in the center of the field of vision. In these more advanced cases, faces and printed words become hard to recognize. As a first symptom of wet AMD, straight lines or edges appear crooked and images become blurred. In some cases this is followed by a central blind spot, as in dry AMD. However, unlike in dry AMD, this vision loss usually occurs rapidly. AMD generally does not affect side vision, even in advanced cases, so patients can function independently.
How is age-related macular degeneration diagnosed?
Your doctor will ask questions about your health history and about any risk factors you might have for AMD. He or she then will perform a thorough eye examination, including tests of visual acuity and, in some cases, an Amsler grid test. An Amsler grid is a drawing of vertical and horizontal lines with a dot in the middle. You are asked to stare at the dot. If you have AMD, some of the lines will appear bent or distorted.
Written and revised by
Gerald Hurowitz, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.