What is Macular Degeneration?
Macular degeneration, also known as age-related macular degeneration (AMD), is a condition that can cause vision loss in the area of the eye responsible for sharp, central vision. Macular degeneration can make everyday activities, such as reading and seeing faces, difficult.
Affecting more than 10 million people in the nation, according to the American Macular Degeneration Foundation, it is the primary cause of vision loss in the United States. In fact, more people have macular degeneration than the eye disorders glaucoma and cataracts combined.
Macular degeneration affects people in all parts of the world. Affecting nearly 1.5 million people in the United Kingdom and almost 1.4 million in Canada, and is the leading cause of blindness in developed countries.
Macular degeneration affects the retina, which is the light-sensitive tissue lining the backside of the eye. Light carries visual information into the eye, where it strikes the retina. The retina absorbs the light and changes the visual information into electrical impulses. The optic nerve at the back of the eye carries these impulses to the brain, which decodes the impulses into a visual image.
Specifically, macular degeneration affects the macula, which sits at the center of the retina. The macula contains the highest concentration of cones, which are light-sensitive cells responsible for providing sharp, detailed central vision. The condition causes the cones to break down, or degenerate, in a way that prevents them from absorbing light correctly.
There are two main forms of AMD, dry and wet, and each has a different cause. Dry macular degeneration occurs when parts of the macula get thin and tiny clumps of protein, known as drusen, grow. Dry AMD is more common – about 80 percent of all people with macular degeneration have the dry form.
Wet AMD is less common but significantly more serious. Vision loss also occurs faster in wet AMD than it does in dry AMD. In wet AMD, abnormal blood vessels grow under the retina. These blood vessels leak blood and other body fluid that can damage and scar the macula.
Certain factors increase the risk for this eye condition. As its name suggests, age is a major factor for age-related macular degeneration. AMD is most likely to occur after the age of 60, although it can develop earlier.
Other factors can increase the risk. Smoking doubles the risk of the disease, for example. A family history of the condition increases the risk, as scientists have identified nearly 20 genes that influence the development of macular degeneration.
Signs and Symptoms
Macular degeneration is a progressive disease, which means it gets worse in time. Sometimes the disease and its symptoms advance so slowly that the vision loss does not happen for a long time. The disease progresses quickly in others.
AMD does not affect vision in its early stages. As the condition progresses, it causes an increasingly blurred area near the center of vision. This blurred area grows larger over time. In some cases, people develop blank spots in their central vision. They may also notice that objects do not seem as bright as they once were. Central vision may ultimately be lost; peripheral vision remains, but it does not provide the clear, detailed vision that central vision does. In some cases, people with very advanced macular degeneration are legally blind.
While macular degeneration does not lead to complete blindness, the loss of central vision can make it hard to do everyday activities. Damage to the macula causes blurry, dark or distorted images in the center of the field of view. Many people with AMD have trouble seeing faces, driving, reading, writing, or performing close work, such as cooking, sewing, or engaging in a favorite hobby. When looking at a clock, for example, someone living with this condition might see the clock’s numbers but not its hands.
There are three main stages:
1. Early AMD
Drusen is present under the retina but most patients do not notice vision loss at this stage.
2. Intermediate AMD
Larger drusen is present in the retina, along with pigment changes; some vision may be lost, but symptoms may not be noticeable.
3. Late AMD
Vision loss becomes noticeable.
Many people do not realize that they have macular degeneration until the damage to the macula has progressed enough to blur their vision. This underscores the importance of regular visits to an eye care professional, who can look for early signs before symptoms develop.
Support and Aids
Eye care professionals use a number of tools to diagnose and manage macular degeneration. Ophthalmologists test for central vision loss with the help of an Amsler grid, a simple square grid with a dot in the middle. The grid will appear to have straight lines for someone with normal vision; it will appear to have wavy lines or spots for someone with macular degeneration.
The eye doctor will also use a special lens to look inside the eye for signs of changes to the macula. The ophthalmologist may perform a fluorescein angiography, a special test that uses yellow dye and a special camera to detect abnormal blood vessels growing in the retina. Some eye care professionals use optical coherence tomography (OCT) machines that provide detailed images of the retina and macula.
There is currently no treatment for dry AMD, although nutritional supplements may slow its progression, according to the American Academy of Ophthalmology. Medications known as anti-VEGF drugs can help treat wet AMD by reducing the number of abnormal blood vessels in the retina and slowing the leakage of blood and other fluids from those blood vessels. Laser surgery may also reduce the presence of abnormal blood vessels and leakage.
Low vision aids can help people with central vision loss see and live independently. Some low vision aids, such as eSight, use high tech cameras, smart algorithms, and high-resolution screen to create clear, real-time images. The innovative combination of cameras, algorithms and high-res screens enhances vision where it people with macular degeneration need it the most – in central vision. Advanced low vision aids help those with AMD read, see faces, do close-up work, and perform many of the other activities of daily living.
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