What is age-related macular degeneration (AMD)? [ 04/29/13 ]
AMD is a common eye disease associated with aging that gradually destroys sharp, central vision. The retina is the very thin tissue that lines the back of the eye and contains the light-sensing cells that send visual signals to the brain. Sharp, clear, 'straight ahead' vision is processed by the macula, which is the central part of the retina. When the macula is damaged, many daily activities such as driving, reading and recognizing faces become increasingly difficult.
Where can I find more information about macular degeneration? [ 04/29/13 ]
The BrightFocus Macular Degeneration Research website goes into greater depth on many of the above topics and covers additional areas of concern, both medical and social. You can learn where to get help and access to resources, as well as download free publications. And explore our Ask an Expert section where you can read or post queries to doctors.
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How many people are estimated to have AMD? [ 04/29/13 ]
Age-related macular degeneration (AMD) is a major cause of visual impairment in the U.S. Age-related macular degeneration (AMD) is a major cause of visual impairment in the United States. As many as 11 million Americans have some form of macular degeneration, including both early and later stages of the wet and dry forms. More than two million people, aged 50 and older, are living with the most advanced forms of the disease.
What are the types of age-related macular degeneration? [ 04/29/13 ]
There are two forms of AMD: dry and wet. It is possible for a person to suffer from both forms and for the disease to progress slowly or rapidly.
Dry macular degeneration is the most common type of AMD. This form, in which the photosensitive cells of the macula slowly break down, is diagnosed in 85 to 90 percent of cases. Yellow deposits called drusen (waste products from metabolism) form and accumulate under the retina, between the retinal pigmented epithelium (RPE) layer and the Bruch's membrane, the blood-retina barrier which supports the retina. Drusen are often found in the eyes of older people, but an increase in the size and number of these deposits is frequently the first sign of macular degeneration. Over time, drusen are associated with deterioration of the macula and the death of RPE and photoreceptor cells, resulting in blurring or a spotty loss of clear, straight-ahead vision.
Dry AMD may advance and cause loss of vision without turning into the wet form of the disease. It is also possible for early-stage dry AMD to change into the wet form of the disease.
Wet macular degeneration is usually preceded by the dry form of the disease. This wet form occurs when the Bruch's membrane begins to break down, usually near drusen deposits, and new blood vessels grow. This growth is called neovascularization. These vessels are very fragile and can leak fluid and blood, resulting in scarring of the macula and the potential for rapid, severe damage. The neovascularization disturbs the natural organization of the light-detecting photoreceptor cells and their associated RPE cells, eventually leading to their death. Straight-ahead vision can become distorted or be lost entirely in a short period of time, sometimes within days or weeks. The wet form accounts for approximately 10 percent of all cases of AMD, but it results in 90 percent of the cases of legal blindness. All wet AMD is considered advanced.
How is AMD diagnosed? [ 04/29/13 ]
To help diagnose AMD, an eye care professional will perform a dilated eye exam to view the retina and optic nerve for damage, a visual acuity test to measure sight from various distances and a fundoscopy to examine the back of the eye. If wet AMD is suspected, fluorescein angiography, in which dye is used to detect leaking blood vessels, may also be performed. The patient might be asked to look at Amsler grid; if the straight lines on the grid appear wavy or distorted, AMD may be developing.
What new research is being done to find a cure for AMD? [ 04/29/13 ]
Researchers continue to explore environmental, genetic and dietary factors that may contribute to developing AMD. New treatment strategies are also being explored, including retinal cell transplants, drugs to prevent or slow down the progress of the disease, radiation therapy, gene therapies, a computer chip implanted in the retina (may help simulate vision) and agents to prevent the growth of new blood vessels under the macula.
Is AMD hereditary? [ 04/29/13 ]
Age-related macular degeneration (AMD) typically affects individuals over 50 years old. Scientific evidence shows that genes may play a role in the development of nearly three out of four cases of this devastating eye disease.
Several genes are believed to be strongly associated with the risk of developing AMD:
- Factor H and Factor B genes are responsible for proteins that help regulate inflammation in the part of the immune system that attacks diseased and damaged cells. According to study results published in 2006 by Columbia University, 74 percent of AMD patients carry certain variants in one or both of these genes, and these may significantly increase their risk of developing it.
- PLEKHA1 – a gene located on chromosome 10; researchers believe it may increase the risk of developing AMD. Like Factors H and B, PLEKHA1 appears to be involved in the cellular processes related to inflammation.
- LOC387715 – A certain variation of this gene appears to increase the risk of developing AMD. This risk is further heightened if a person with this gene variation also smokes.
- HTRA1 – Scientists have identified a link between a mutation in this gene and the development of AMD. Specifically, the HTRA1 mutation is thought to be associated with the formation of drusen (yellow deposits of waste products under the retina that are often a sign of dry AMD), and may also promote the growth of fragile new blood vessels typical of wet AMD.
- Complement C3 – Researchers have found that a variant in this gene increases the risk of developing the wet and dry forms of AMD. This gene plays an important role in the immune system, leading scientists to believe that inflammation is a vital part of the AMD disease process.
Other gene candidates are being studied to determine their role in AMD. While there is definitely a strong genetic component to this disease, it is highly likely that its development is due to a combination of multiple factors including gene mutations or variations and environmental factors such as sunlight exposure, diet and smoking.
Can diet prevent AMD? [ 04/29/13 ]
Some limited studies appear to indicate that eating a diet high in carotenoids, antioxidant vitamins (such C and E), and omega-3 fatty acids may reduce the risk of developing age-related macular degeneration (AMD); however, more research is required before definitive statements can be made.
Carotenoids are compounds that are found in plants, which have been associated with protection not only from macular degeneration, but from cancer, heart disease, diabetes, and a number of other medical conditions. Dark green, yellow and orange fruits and vegetables, especially those high in the carotenoids known as lutein and zeaxanthin, appear to provide the best protection for AMD. Lutein and zeaxanthin are the primary pigments in the macula and are thought to protect the retina from ultraviolet light.
Lutein is found in spinach, collard greens, kale, broccoli, papaya, oranges, mango, green beans, peaches, sweet potatoes, lima beans, squash, red grapes, and green bell pepper. Yellow corn, squash, oranges, mango, kale, apricots, peaches, and orange bell pepper are good sources of zeaxanthin.
Foods abundant in vitamin C include green peppers, citrus fruits, tomatoes, broccoli, strawberries, yams, leafy greens, and cantaloupe.
Vitamin E is found in eggs, fortified cereals, fruit, wheat germ, green leafy vegetables, nuts/nut oils, vegetable oils, and whole grains.
Wild salmon, sardines, walnuts, and flaxseed oil are good sources of omega-3 fatty acids.