Ageing (Senile) Macular Degeneration:
Macular degeneration is the progressive deterioration of the macula, the small central area of the retina. The central macula, the fovea, is responsible for fine-detail vision and has the highest concentration of color receptors (i.e., cone cells).
The most common type of macular degeneration is called age-related macular degeneration (AMD), because it usually develops in patients over the age of 55. A rare form of macular generation, called juvenile macular degeneration (JMD), occurs in younger patients, including infants and children. JMD is an inherited disorder caused by mutated genes.
Incidence and Prevalence
Macular degeneration is diagnosed every 3 minutes in the United States. It occurs in about 10% of people over the age of 50, and about 33% of people over 75. AMD is most common in Caucasians of European decent and is more prevalent in women. Every year 1.2 million people with macular degeneration lose part of their central vision, and 200,000 suffer complete loss of central vision in one or both eyes.
Types
Age-Related Macular Degeneration
Because AMD primarily affects central vision, patients usually do not lose vision completely, even at very advanced stages. This disorder can make it difficult to read, drive, work at a computer, and perform other activities that require clear central vision. AMD occurs in two forms, dry and wet.
Dry (atrophic) This form of AMD accounts for 85–90% of all cases. The earliest sign of AMD is the development of waste material deposits, called drusen, that appear as tiny orange or yellow dots among the retinal epithelial (RPE) cells. These deposits are initially tiny and few in number, but they may grow larger and become more numerous. The presence of drusen does not necessarily signal vision loss, and many people with drusen continue to have good vision for decades. As dry AMD progresses, mild to moderate visual acuity loss may occur.
Over time, patches of RPE cells may die, leaving "bare" spots. This is called geographic atrophy and results in vision loss in the affected areas of the retina. If these patches become large and involve the fovea, visual acuity can deteriorate to the point of legal blindness. Geographic atrophy is a severe form of dry macular degeneration.
Wet (vascular) The wet form accounts for approximately 10% of cases but is responsible for the vast majority of severe, AMD-related vision loss. Vascular macular degeneration begins as the dry form and progresses to the wet form when abnormal blood vessels develop. In wet AMD, abnormal blood vessel growth is triggered by mechanisms that are not completely understood. The new vessels are very delicate, break easily, and bleed and leak fluid into surrounding tissue. This can damage the macula very quickly and may cause central vision loss in a short time. The risk for progression from dry to wet AMD is approximately 14-87% over 5 years and depends on many factors.
What is macular degeneration?
Macular degeneration is the physical disturbance of the center of the retina called the macula. The macula, which is about the size of the capital letter "O" in this sentence, is the part of the retina which is capable of our most acute and detailed vision. We use the macula for reading, driving, recognizing faces, watching television, and fine work. Macular degeneration is the leading cause of legal blindness in people over age 55. (Legal blindness means that a person can see 20/200 or less with eyeglasses.) Even with a loss of central vision, however, color vision and peripheral vision may remain clear. Vision loss usually occurs gradually and typically affects both eyes at different rates.
What causes macular degeneration?
The root causes of macular degeneration are still unknown. There are two forms of age-related macular degeneration, "wet" and "dry". Seventy percent of patients have the "dry" form, which involves thinning of the macular tissues and disturbances in its pigmentation. Thirty percent have the "wet" form, which can involve bleeding within and beneath the retina, opaque deposits, and eventually scar tissue. The "wet" form accounts for ninety percent of all cases of legal blindness in macular degeneration patients.
Different forms of macular degeneration may occur in younger patients. These non-age related cases may be linked to heredity, diabetes, nutritional deficits, head injury, infection, or other factors. The Schepens scientists are undertaking the basic research necessary to determine the causes of these disorders. Finding the cause is the first important step toward prevention and cure.
How is macular degeneration detected?
Declining vision noticed by the patient or by an ophthalmologist during a routine eye exam may be the first indicator of macular degeneration. The formation of new blood vessels and exudates, or "drusen," from blood vessels in and under the macular is often the first physical sign that macular degeneration may develop. In addition, the following signs may be indicative of macular problems. Anyone experiencing these symptoms should consult an ophthalmologist immediately:
Straight lines appear distorted and, in some cases, the center of vision appears more distorted than the rest of the scene.
Blurry area or "white-out" appears in the center of vision.
Color perception changes or diminishes.
The following are NOT known to be linked to macular degeneration: floaters (moving spots caused by debris floating in the vitreous fluid between the lens and the retina); dry eye syndromes; cataracts and cataract surgery.
Is early detection important?
Early detection is important because a patient destined to develop macular degeneration can sometimes be treated before symptoms appear, and this may delay or reduce the severity of the disease. Furthermore, as we develop better treatments for macular degeneration, whether they are medicinal, surgical, or low vision aids, those patients diagnosed with macular degeneration can sooner benefit from them.
If I have macular degeneration in one eye, will it develop in the other?
Yes, this is usually the case. In the early stages, only one eye may be affected, but as the disease progresses, both eyes are usually affected.
Is there a cure for Macular Degeneration?
At this time there is no known cure for macular degeneration. In some cases, macular degeneration may be active and then slow down considerably, or even stop progressing for many, many years. One day, research may show us how to prevent and reverse the disease. Today, there are ways to arrest macular degeneration, depending on the type and the degree of the condition. These range from nutritional intervention to laser surgery of the blood vessels (see below). We also have developed low vision aids and techniques for maximizing the use of peripheral vision to help patients adapt better to their loss of central vision. Educating susceptible groups about macular degeneration can enhance early detection and early treatment. We advise that a patient select and eye center that specializes in macular degeneration and get opinions for treatment from retina specialists.
Can nutrition help treat macular degeneration?
Some scientists have suggested an association between macular degeneration and high saturated fat, low carotenoid pigments, and other substances in the diet. There is evidence that eating fresh fruits and dark green, leafy vegetables (such as spinach and collard greens) may delay or reduce the severity of age-related macular degeneration. Taking anti-oxidants like Vitamins C and E may also have positive effects. Zinc, however, has shown mixed results. In some people, the long-term use of zinc causes digestive problems and anemia; its use is probably not worth the potential problems. Selenium is sometimes recommended, but you should always consult your physician to determine appropriate dosages. The Schepens is committed to continued research in nutrition and its effect on macular degeneration.
Can surgery help cure macular degeneration?
Surgery to remove the scar produced by macular degeneration has been successful in younger patients, but less successful in older patients. If the degeneration is associated with leaking blood vessels in the center of the macula, and vision is worse than 20/70, laser surgery, called photocoagulation, is recommended. This will not improve vision but generally reduces further vision loss. Retinal transplantation is a new experimental approach to macular degeneration, but will require at least 3 - 5 years of clinical research at The Schepens and other centers to determine its safety and effectiveness.
Is macular degeneration hereditary?
Macular degeneration appears to be hereditary in some families but not in others. Since macular degeneration affects most patients later in life, it is difficult to study successive generations in a family. Recent studies of twins indicate that both genetic and non-genetic factors play important roles in age-related macular degeneration. Research to determine the genes associated with hereditary macular degeneration will help lead to early detection, early intervention, and possible cures.
What can I do to help prevent and cure macular degeneration?
Have annual routine eye exams
See your ophthalmologist without delay if you notice any decline in your vision
Does sunlight affect macular degeneration?
Yes. It has been demonstrated that the blue rays of the spectrum seem to accelerate macular degeneration more than other rays of the spectrum. This means that very bright light, such as sunlight or its reflection in the ocean and desert, may worsen macular degeneration. Special sunglasses that block out the blue end of the spectrum may decrease the progress of the disease. Again, more research is needed in this area.
Does hypertension (or medication for hypertension) affect macular degeneration?
Yes. Hypertension tends to make some forms of macular degeneration worse, especially in the "wet" form where the retinal tissues are invaded by new blood vessels. The medications used to treat hypertension have not been shown to have any direct effect on macular degeneration, but they may slow progression of the disease by reducing hypertension.
Does smoking or second hand smoke contribute to macular degeneration?
Yes. Any type of smoking or exposure to tobacco smoke can accelerate the development of the "wet" type of macular degeneration.
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