Macular degeneration is a disease of the eye that doesn't lead to total blindness, but in its advanced stages can cause blind areas. This can make it hard for people to read, recognize faces and perform other tasks.
Dr. Janet Sunness, a low vision and retina specialist and medical director of Greater Baltimore Medical Center's Hoover Low Vision Rehabilitation Services, talks about how to diagnose and treat macular degeneration.
What is macular degeneration?
Age-related macular degeneration is the leading cause of severe visual loss in the population over the age of 65. The disease causes weakening of the macula, which is the small area at the center of the retina, which is specialized for fine vision. In its early stages, macular degeneration causes only a mild reduction of vision and a need for good lighting. In its advanced stages, it causes blind areas in the central vision, leading to difficulties with reading, recognizing faces and performing other fine tasks. It does not typically affect the peripheral vision, so patients do not usually have difficulty walking around.
People over the age of 75 are at greater risk for getting the disease, and it is much more common in Caucasian people than in African-Americans. A family history of macular degeneration increases the risk of getting the disease. Smoking is a risk factor for more rapid development of the advanced forms.
How is it detected and why is it hard to detect?
Macular degeneration is easy to detect by an ophthalmologist or optometrist, and it's done by examining the retina and imaging it with special devices. In the early stages of dry macular degeneration, there are yellow deposits, called drusen, under the retina, which is the nerve tissue that lines the inside of the eye that detects light and sends nerve fibers to the brain. People who have large drusen are more likely to go on and develop the advanced forms of macular degeneration.
Advanced dry macular degeneration has blind areas where there is a dropout of the normal retinal cells. Wet macular degeneration involves abnormal new blood vessels under the retina that leak and bleed and can cause scarring and loss of vision. The terminology is often confusing, because dry macular degeneration includes people with good vision who may never lose vision, as well as people with advanced dry macular degeneration who are legally blind.
Early (dry) macular degeneration is often asymptomatic. But people may not be aware of developing advanced macular degeneration in just one eye. If one eye sees well, a person may not notice that the other eye has lost vision unless he or she happens to close the better-seeing eye.
There has been a dramatic improvement in treatment for wet macular degeneration since 2005. Current treatment is injection of a drug into the white part of the eye that blocks the stimulus for new blood vessel growth. This treatment is very effective in stabilizing and sometimes improving vision and, unlike the past, few treated patients have become legally blind. However, the injections must be given every four to eight weeks over a prolonged period of time for many patients.
There is no treatment currently for advanced dry macular degeneration. For people who do not have advanced macular degeneration, but have high risk characteristics for developing it, there is a combination of vitamins and minerals, called the AREDS medication, which reduces the risk of developing wet macular degeneration by about 25 percent.
Low-vision rehabilitation can be of great value to patients with macular degeneration. Better lighting, stronger reading glasses and perhaps a low-power magnifier may be enough to return a patient with moderate visual loss to reading and other activities. For patients with more severe visual loss, there are stronger glasses and magnifiers, digital video magnifiers and techniques for compensating for blind spots in the vision that can be provided by an occupational therapist or other low vision rehabilitation provider. Mainstream technology, such as iPhones, iPads and other tablets, as well as computers, provide for magnification, increased contrast and text-to-speech.
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Macular degeneration affects central vision. It is very rare for it to involve the peripheral retina and it does not cause total blindness. It may cause legal blindness, defined as requiring letters 10 times the normal size (20/200). It is important for people to know that about 20 percent of patients with vision loss from macular degeneration experience visual hallucinations. That means that they see things that are not there. They may see patterns, people, animals, flowers, houses or other things. Fortunately, people don't experience the hallucinations as being frightening. They probably result from the brain trying to compensate for what is not being seen by the eye. Many patients with this are worried that they are going crazy, and are relieved to learn that the hallucinations may just be a consequence of the macular degeneration.
Is there a way to prevent it?
There are a few things one can do to reduce the risk of getting advanced macular degeneration and visual loss. Stop smoking. Eat a diet abundant in richly colored vegetables, such as red peppers or spinach, which contain lutein and zeaxanthin and other micronutrients. Wearing sunglasses is probably beneficial, but this is over the whole course of life, not just in later years. If there is a strong family history of macular degeneration, get examined every year or two beginning at age 50, and take the AREDS medication if indicated.