Risk Factors (Genetics & Inherited Conditions)
The risk for macular degeneration increases with age and is most commonly seen in senior citizens. Individuals who have family members with macular degeneration, who are white, and who smoke are also at risk. Women are possibly at an increased risk. Other risk factors include high blood pressure and high cholesterol.
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Etiology and Genetics (Genetics & Inherited Conditions)
Macular degeneration is a complex condition that involves a wide range of genetic and environmental contributing factors. It is not surprising, therefore, that no reliable predictions can be made with regard to inheritance patterns for this condition. Autosomal recessive inheritance is suggested for some contributing genes, and autosomal dominant inheritance is indicative for others, yet the best that can be said about predictive patterns is that age-related macular degeneration tends to run in families.
The gene that is identified most frequently with macular degeneration is the CFH gene, which specifies the complement factor H protein. Found on the long arm of chromosome 1 at position 1q31-q32.1, specific mutations in this gene have been reported in perhaps as many as 50 percent of cases. This mutational variant, however, is also found in some unaffected individuals, so it apparently increases the likelihood of an individual developing the disease rather than being a definitive cause by itself. Interestingly, other investigators report a different mutational variant in this gene that serves to reduce the risk of developing the disease. Mutations in two other genes that specify components of the complement pathway are also associated with reduced risk (CFB and C2, both found in a gene cluster at position 6p21.3). Other genes that have been associated with some cases of macular degeneration...
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Symptoms (Genetics & Inherited Conditions)
In some people, AMD advances very slowly, and it has little effect on their vision. In others, the disease progresses faster, and it may lead to significant vision loss. Neither dry nor wet AMD causes pain.
Symptoms include blurred vision; difficulty seeing details in front of the individual, such as faces or words in a book; blurred vision that goes away in brighter light; having a small, but growing blind spot in the middle of the field of vision; and seeing straight lines, such as door frames, as appearing crooked or distorted.
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Screening and Diagnosis (Genetics & Inherited Conditions)
The doctor will ask about a patient’s symptoms and medical history, and a physical exam will be done. The doctor may suspect AMD if a patient is older and has had recent changes in his or her central vision. A specialist will look for signs of the disease. He or she will use eye drops to dilate (enlarge) a patient’s pupils, which will allow the specialist to view the back of the eye.
A patient may also be asked to view an Amsler grid. This is a pattern that looks like a checkerboard. Changes in a patient’s central vision will cause the grid to appear distorted, which is a sign of AMD.
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Treatment and Therapy (Genetics & Inherited Conditions)
Research has shown that certain high-dose vitamins and minerals may slow the progression of dry AMD in some patients.
Laser photocoagulation is used in some cases of wet AMD. In this procedure, a strong laser light beam is aimed onto the new blood vessels. The beam will destroy the vessels. It usually takes less than thirty minutes to complete this procedure. Patients may need additional laser treatments. This treatment is used less often since the development of newer treatments.
Photodynamic therapy, another type of treatment for wet AMD, involves injecting a light-sensitive dye into the blood. The affected areas in the back of the eye are then hit with a special laser light. The light activates the dye to destroy certain blood vessels. This treatment also takes less than thirty minutes. A patient may need to have additional treatments.
Another treatment for wet AMD is an injection of a special medication called a vascular endothelial growth factor (VEGF) inhibitor. This medicine is injected into the vitreous (fluid) in the back of the eye. This method is quickly growing in popularity. It usually needs to be repeated multiple times, and, in rare cases, it may need to be given indefinitely. About one-third of patients will show significant improvement in vision. This is the first treatment to show improved vision in a significant number of patients.
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Prevention and Outcomes (Genetics & Inherited Conditions)
There are no guidelines for preventing AMD. For overall eye health, individuals should have comprehensive exams of their eyes regularly. These exams should include dilation to look closely at the retina. Individuals can also improve overall eye health if they do not smoke, consider taking a multivitamin with antioxidants every day, and consider taking omega-3 fatty acid supplements.
If patients have AMD, their doctors may advise them to monitor for problems by using an Amsler grid at home. Their ophthalmologists can discuss the various treatment options with them.
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Further Reading (Genetics & Inherited Conditions)
EBSCO Publishing. Health Library: Macular Degeneration. Ipswich, Mass.: Author, 2009. Available through http://www.ebscohost.com.
Lim, Jennifer I., ed. Age-Related Macular Degeneration. 2d ed. New York: Informa Healthcare, 2008.
Mogk, Lylas G., and Marja Mogk. Macular Degeneration: The Complete Guide to Saving and Maximizing Your Sight. Rev. ed. New York: Ballantine, 2003.
Rosenfield, P. J., et al. “Ranibizumab for Neovascular Age-Related Macular Degeneration.” New England Journal of Medicine 335, no. 14 (October 5, 2006): 1419-1431.
Wormald, R., et al. “Photodynamic Therapy for Neovascular Age-Related Macular Degeneration.” Cochrane Database of Systematic Reviews. Available through EBSCO DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/dynamed.
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Web Sites of Interest (Genetics & Inherited Conditions)
AMD Alliance International. http://amdalliance.org
American Macular Degeneration Foundation. http://www.macular.org
Macular Degeneration Foundation. http://www.eyesight.org
The National Coalition for Vision Health. http://www.visionhealth.ca
National Eye Institute. http://www.nei.nih.gov
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Causes and Symptoms (Magill’s Medical Guide, Sixth Edition)
The macula is located in the center of the retina, the light-sensitive tissue at the back of the eye. The retina instantly converts light, or an image, into electrical impulses. The retina then sends these impulses, or nerve signals, to the brain. One of the earliest signs of age-related macular degeneration (ARMD) seen by physicians during a dilated eye examination is deposits of tiny, bright yellow material called drusen, which is harder as a result of aging or softer and larger if associated with ARMD and vision loss. As parts of the eye in the retina and choroid become thinner or lose tissue, central vision and/or peripheral vision is affected, depending on the area of damage. Central vision is needed to see clearly and to perform everyday activities such as reading, writing, driving, and recognizing people and things. Peripheral vision, needed for walking, is much less commonly affected.
There are two forms of ARMD: early and advanced. About 90 percent of cases are early ARMD, although the advanced type affects 7 percent of those seventy-five years or older. Advanced ARMD is further categorized into two distinct types based on their clinical features: dry and wet. The dry form involves thinning of the macular tissues and disturbances in its pigmentation. About 70 percent of patients have the dry form. The remaining 30 percent have the wet form, which can involve bleeding within and beneath the retina, opaque...
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Treatment and Therapy (Magill’s Medical Guide, Sixth Edition)
New and exciting treatments are in development for ARMD as extensive research is being done. Currently, there is no cure, and no treatment recommendations exist for those with dry type ARMD, the type that is much less threatening to vision. Some treatments, however, can slow the progression of wet type ARMD. Research has shown that stopping smoking is the most effective preventive measure in regard to developing ARMD and slowing its progression.
Antioxidants have proved promising in recent studies which show that they can lower the risk of progression to more advanced ARMD in those who have moderate or advanced disease. In a major clinical trial called the Age-Related Disease Study (AREDS), it was shown that patients with moderate or severe ARMD taking antioxidants vitamin C, vitamin E, and beta carotene plus zinc and copper had a lower risk of progression among both nonsmokers and smokers. Since the group of smokers who took zinc alone had the same lowered risk of progression as those smokers taking antioxidants plus zinc and copper, it was recommended that smokers with ARMD take zinc alone, as some antioxidants have shown to increase the risk of lung cancer and coronary heart disease when used at high doses.
Although no treatments can reverse the actual pathologic process of the disease of wet type ARMD, some treatments used by ophthalmologists are aimed at containing the damaged vessels that cause the loss of...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Blindness or low vision affects 3.3 million Americans aged forty and over, or one in twenty-eight, according to the Eye Disease Prevalence Research Group study, sponsored by the National Eye Institute. This figure is projected to reach 5.5 million by the year 2020. The study reports that low vision and blindness increase significantly with age, particularly in people over age sixty-five. People eighty years of age and older currently make up 8 percent of the population but account for 69 percent of blindness. ARMD affects about 15 percent of the U.S. population by age fifty-five and more than 30 percent by age seventy-five. It is the most common cause of legal blindness in people over the age of sixty-five.
Although there is no cure for ARMD, many treatments are available to curtail progression of the disease. As extensive research continues in this area, advances in the diagnosis and treatment of this debilitating condition are anticipated by many in the field of ophthalmology. Currently, the National Eye Institute is studying the possibility of transplanting healthy cells into a diseased retina, evaluating families with a history of ARMD to understand genetic and hereditary factors that may cause the disease, and looking at certain anti-inflammatory treatments for the wet form of ARMD.
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
American Macular Degeneration Foundation. http://www.macular.org. Provides information to clinicians and patients regarding the latest in research regarding ARMD. Offers an award-winning video for helping patients with ARMD cope with this debilitating illness.
D’Amato, Robert, and Joan Snyder. Macular Degeneration: The Latest Scientific Discoveries and Treatments for Preserving Your Sight. New York: Walker, 2000. Ophthalmologist and noted researcher D’Amato teams up with macular degeneration patient Snyder to write a reassuring, hopeful, and informative book providing the facts that sufferers need in order to understand the disorder, handle treatment options, and live successfully with low vision.
Kansai, Jack. Diseases of the Macula. New York: Elsevier, 2002. A clinical text that covers diseases that primarily affect the macula, such as age-related macular degeneration, together with secondary diseases that might have an indirect effect on macular function, such as vascular and inflammatory disorders.
Macular Degeneration Foundation. http://www.eye sight.org. Describes this charitable educational and research foundation dedicated to discovering the cause of and developing cures for macular degeneration.
MayoClinic.com. “Macular Degeneration.” http://www.mayoclinic.com/health/macular-degeneration/DS00284. Provides a comprehensive overview of the risk factors, symptoms,...
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Macular Degeneration (Encyclopedia of Medicine)
Macular degeneration is the progressive deterioration of a critical region of the retina called the macula. The macula is a 3-5 mm area in the retina that is responsible for central vision. This disorder leads to irreversible loss of central vision, although peripheral vision is retained. In the early stages, vision may be gray, hazy, or distorted.
Macular degeneration is the most common cause of legal blindness in people over 60, and accounts for approximately 11.7% of blindness in the United States. About 28% of the population over age 74 is affected by this disease.
Age-related macular degeneration (ARMD) is the most common form of macular degeneration. It is also known as age-related maculopathy (ARM), aged macular degeneration, and senile macular degeneration. Approximately 10 million Americans have some vision loss that is due to ARMD.
ARMD is subdivided into a dry (atrophic) and a wet (exudative) form. The dry form is more common and accounts for 70-90% of cases of ARMD. It progresses more slowly than the wet form and vision loss is less severe. In the dry form, the macula thins over time as part of the aging process and the pigmented retinal epithelium (a dark-colored cell layer at the back of the eye) is gradually lost. Words may appear blurred or hazy...
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Macular Degeneration (Encyclopedia of Alternative Medicine)
Macular degeneration (MD) is the progressive deterioration of the macula, the light-sensitive cells of the central retina, at the back of the eye. The retina is the sensitive membrane (soft layer) of the eye that receives the image formed by the lens and is connected with the brain by the optic nerve. As these macular cells malfunction and die, central vision becomes gray, hazy, or distorted, and eventually is lost. Peripheral (away from the center) vision is unaffected.
Millions of people suffer from MD and it accounts for about 12% of all blindness in the United States. The macula contains the highest concentration of photosensitive cells in the retina. These cells transform light into electrical signals that are sent to the brain for processing into vision. Fine detail vision and critical color vision are located in the macula. The macula depend on nutrient diffusion from the choroid layer, a region of several delicate vascular (pertaining to blood vessels) membranes or structures behind the retina and under the macula. Anything that interferes with this nutrient supply can lead to MD.
Age-related macular degeneration (AMD or ARMD) is by far the most common type of MD. One in six Americans develops AMD between the ages of 55 and 64 and one in three Americans over 75 has AMD. About 10% of...
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Macular Degeneration (Encyclopedia of Nursing & Allied Health)
Macular degeneration is the progressive deterioration of a critical region of the retina called the macula. The macula is 3 mm and is responsible for central vision. This disorder leads to irreversible loss of central vision, although peripheral vision is retained. In the early stages, vision may be gray, hazy, or distorted.
Macular degeneration is the most common cause of legal blindness in people over 60, and accounts for approximately 11.7% of blindness in the United States. About 28% of the population over age 74 is affected by this disease.
Age-related macular degeneration (ARMD) is the most common form of macular degeneration. It is also known as age-related maculopathy (ARM), aged macular degeneration, and senile macular degeneration. Approximately ten million Americans have some vision loss due to ARMD.
ARMD is subdivided into a dry (atrophic) and a wet (exudative) form. The dry form is more common and accounts for 700% of cases of ARMD. It progresses more slowly than the wet form and vision loss is less severe. In the dry form, the macula thins over time as part of the aging process and the pigmented retinal epithelium (a dark-colored cell layer at the back of the eye) is gradually lost. Words may appear blurred or hazy, and colors may appear dim or gray.
With wet ARMD, new blood vessels grow underneath the retina and distort the retina. These blood vessels can leak, causing scar tissue to form on the retina. The wet form may cause visual distortion and make straight lines appear wavy. A central blind spot develops.
The wet type progresses more rapidly and vision loss is more pronounced.
Less common forms of macular degeneration include:
- Cystoid macular degeneration: Vision loss in the macula due to fluid-filled areas (cysts) in the macular region. This may be a result of other disorders, such as aging, inflammation, or high myopia.
- Diabetic macular degeneration: Deterioration of the macula due to diabetes.
- Senile disciform degeneration (Kuhnt-Junius macular degeneration): A severe type of wet ARMD that involves hemorrhaging in the macular region. It usually occurs in people over 40 years old.
Causes and symptoms
Age-related macular degeneration is intrinsic to aging for some individuals, but not all. People with an ARMD-affected family member have an increased the risk for its development. A slightly higher incidence occurs in females, although males and females are considered to be equally at risk. Whites and Asians are more susceptible to developing ARMD than blacks, in whom the disorder is rare.
The cause of ARMD is thought to be arteriosclerosis in the blood vessels supplying the retina. Certain risks for the heart are considered similar risks to those that contribute to the development of macular degeneration. Smoking increases the risk of developing wet-type ARMD, and may increase the risk of developing dry-type as well. Dietary fat also increases the risk. In one study of older (age 454) Americans, signs of early ARMD were 80% more common in the group who ate the most saturated fat compared to those who ate the least. Low consumption of antioxidants, such as foods rich in vitamin A, is associated with a higher risk. It is generally believed that exposure to ultraviolet (UV) light may contribute to disease development, but this has not been proven conclusively.
A study reported in Ophthalmology in 2000 concluded that hypertension, thyroid hormones, and antacids are associated with certain types of ARMD. The issue of antacids is not widely recognized since no determination has yet been made regarding whether the antacids themselves lead to the disease, or whether it is the stomach problems that are a contributing factor. Obesity was also found to be a factor in this study.
The main symptom of macular degeneration is a central vision change. The patient may experience blurred central vision or a blank spot on the page when reading, visual distortion such as bending of straight lines, and images might appear smaller than is the actual object. Some patients notice a change in color perception, or abnormal light sensations. These symptoms can emerge suddenly and become progressively worse. Patients should be advised that a sudden onset of symptoms, particularly vision distortion, is an indication for immediate evaluation.
Optometrists and ophthalmologists, with assistance from ophthalmic assistants, technicians and nurses, should carefully screen patients who are at risk for macular degeneration. These include patients older than 60; patients with hypertension or cardiovascular disease; cigarette smokers; patients with a first-degree family (sibling or maternal) history of vision loss from ARMD regardless of age; patients with aphakia or pseudophakia; or someone with a cataract, and patients with a history that indicates significant cumulative light exposure.
The ophthalmic assistant will take a careful history and log these risk factors. The patient then should have a complete ocular examination. Vision tests, performed by the physician or a skilled ophthalmic assistant, examine best corrected visual acuity, as well as near monocular visual acuity; refraction; biomicroscopy; tonometry; and stereoscopic fundus examination with pupillary dilation. Though rarely used even if ARMD is suspected, a central 10-degree computerized automated perimetry might be utilized along with fundus photography and laser ophthalmoscope scanning.
After preliminary testing, specific tests are performed to determine macular degeneration. To make the diagnosis, the doctor dilates the pupil with eye drops and examines the interior of the eye, examining the retina for the presence of drusen, small white-yellow spots in the macular area, and for gross changes in the macula such as thinning. The doctor also administers a visual field test to search for blank spots in the central vision. The doctor might order fluorescein angiography (intravenous injection of fluorescent dye followed by visual examination and photography of the back of the eye) to determine if blood vessels in the retina are leaking. Retinal pigmented epithelium (RPE) mottling that occurs, like the drusen, due to ateriorsclerotic changes of the macula decreasing the blood supply, can also be indicated through a thorough examination.
A central visual field test called an Amsler grid is usually given to patients who are suspected of having ARMD. It is a grid printed on a sheet of paper (also presented for home use every week). When viewing a central dot on the page, the patient should note if any of the lines appear to be wavy or missing. This could be an indication of fluid and the onset of wet ARMD. High-risk patients particularly will be urged to schedule more frequent checkups.
Although ophthalmologists and optometrists can accurately diagnose macular degeneration, attending physicians may want to consult with a retinal specialist for the best treatment protocols.
While vision loss cannot be reversed, early detection is important because treatments are available that may halt or slow the progression of the wet form of ARMD. Some treatments for the dry form were still in early clinical trials in 2001.
In wet-type ARMD and in senile disciform macular degeneration, new capillaries grow in the macular region and leak. This leaking of blood and fluid causes a portion of the retina to detach. Blood vessel growth, called neovascularization, can be treated with laser photocoagulation in some cases, depending upon the location and extent of the growth. Argon or krypton lasers can destroy the new tissue and flatten the retina. This treatment is effective in about half the cases but results may be temporary. A concern exists that laser therapy causes the laser to destroy the photoreceptors in the treated area. If the blood vessels have grown into the fovea (a region of the macula responsible for fine vision), treatment may be impossible. Because capillaries can grow quickly, this form of macular degeneration should be handled as an emergency and treated immediately.
Photodynamic therapy (PDT) is a promising new treatment approved by the Food and Drug Administration in 2000. With PDT, the patient is given a light-activated drug intravenously with no damage to the retina. The drug, Visudyne, is absorbed by the damaged blood vessels. The affected area on the retina is exposed to a nonthermal laser light that activates the drug exactly 15 minutes after the infusion begins. It must be exactly 15 minutes for the treatment to be successful. The light chemically alters the drug, and any leakage from choroidal neovascularization (CNV) ceases. Patients require treatment every three months during the first year of therapy, and should be advised to avoid bright light or sun exposure for several days after therapy.
Another form of treatment for the wet form of ARMD is radiation therapy with either x rays, or a proton beam. Growing blood vessels are sensitive to treatment with low doses of ionizing radiation. The growth of nerve cells in the retina is stunted. They are insensitive and thus are not harmed by this treatment. External beam radiation treatment has shown promising results at slowing progression in limited, early trials.
Other therapies that are under study include treatment with alpha-interferon, thalidomide, and other drugs that slow the growth of blood vessels. Subretinal surgery also has shown promise in rapid-onset cases of wet ARMD. This surgery carries the risk of retinal detachment, hemorrhage, and acceleration of cataract formation. A controversial treatment called rheotherapy involves pumping the patient's blood through a device that removes some proteins and fats. As of 2001, this had not been proven to be safe or effective.
Consumption of a diet rich in antioxidants (beta carotene and the mixed carotenoids that are precursors of vitamin A, vitamins C and E, selenium, and zinc), or antioxidant nutritional supplements, may help prevent macular degeneration, particularly if started early in life. Research has shown that nutritional therapy can prevent ARMD or slow its progression once established.
Researchers also are working on therapies to treat the dry form of macular degeneration. Low-energy laser treatment for drusen is currently in clinical trials as of 2001. In this treatment the ophthalmologist uses a diode laser to reduce the drusen level. Some ophthalmologists were already performing this procedure "off-label," without FDA approval.
Another treatment, approved overseas but not in the United States, treats dry ARMD by implanting a miniaturized telescope to magnify objects in the central field of vision. This does not treat the disease, but aids the patient's vision in only the very severe cases of ARMD.
The dry form of ARMD is self-limiting and eventually stabilizes, with permanent vision loss. The vision of patients with the wet form of ARMD often stabilizes or improves even without treatment, at least temporarily.
However, after a few years, patients with this type are usually left without acute central vision.
Many macular degeneration patients lose their central vision permanently and may become legally blind. However, macular degeneration rarely causes total vision loss. Peripheral vision is retained. Patients can compensate for central vision loss, even when macular degeneration renders them legally blind. Improved lighting and low-vision aids can help even if visual acuity is poor. Vision aids include special magnifiersallowing patients to read, and provide telescopic aids for long-distance vision. The use of these visual aids plus the retained peripheral vision assist in maintaining patient independence.
Health care team roles
Ophthalmic assistants, technicians, and nurses assist optometrists and ophthalmologists in testing for macular degeneration. Skilled ophthalmic staff take patient history and perform refraction; biomicroscopy; tonometry; stereoscopic fundus examination with pupillary dilation, only rarely; computerized automated perimetry; and fundus photography.
Registered ophthalmic nurses also play an important role in preparing patients for PDT. Only registered nurses and physicians are allowed to mix the drug used for PDT. RNs familiar with infusion are best-suited for this task. Nurses and ophthalmic staff also play an important role in PDT follow-up care. They are critical in issuing patient instructions to stay out of bright light and sunlight after treatment, and to wear sun-protective clothing for each treatment.
Ophthalmic staff should reinforce the physician's instructions when assessing macular degeneration. They
should emphasize the importance of the Amsler grid and regular check-ups to monitor the progression of the disease.
Staff should also reaffirm doctor's orders with patients being treated with PDT. They should review that PDT is not a cure, but a slowing of the disease, and that retreatment is necessary for its success. Staff should also reinforce restrictions on patients' activities, such as staying out of direct sunlight or bright light for several days after PDT. They should also make follow-up calls to patients to ensure they are returning for PDT on time and to see if they have any questions about retreatment. Ophthalmic personnel should also be considerate of the age of most macular degeneration patients and provide large, easy-to-read instructions, and not rush them through the therapy or aftercare.
Avoiding the risk factors for macular degeneration may help prevent it. This includes avoiding tobacco smoke and eating a diet low in saturated fat and rich in antioxidants. Some doctors suggest that wearing UV-blocking sunglasses reduces risk. Use of estrogen in post-menopausal women is associated with a lower risk of developing ARMD.
Druseniny yellow dots on the retina that can be soft or hard and that usually do not interfere with vision.
Fovea tiny pit in the macula that is responsible for sharp vision.
Neovascularizationrowth of new capillaries.
Photoreceptorspecialized nerve cells (rods and cones) in the retina that are responsible for vision.
Retinahe light-sensitive membrane at the back of the eye that images are focused on. The retina sends the images to the brain via the optic nerve.
Norris, June, ed. Professional Guide to Diseases, 5th ed. Springhouse, PA: Springhouse Corporation, 1995.
Tierney, Lawrence M. Jr., Stephen J. McPhee, and Maxine A. Papadakis, eds. Current Medical Diagnosis and Treatment, 37th ed. Stamford, CT: Appleton and Lange, 1998.
American Academy of Ophthalmology (National Eyecare Project). P.O. Box 429098, San Francisco, CA. 94142-9098. (800)222-EYES. <<a href="http://www.eyenet.org">http://www.eyenet.org>.
American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. <<a href="http://www.aoanet.org">http://www.aoanet.org>.
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Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. <<a href="http://www.prevent-blindness.org">http://www.prevent-blindness.org>.
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Macular Degeneration" Optometric Management Online <<a href="http://www.optometric.com/archive_results.asp?loc=archive/0314200011121pm.html">http://www.optometric.com/archive_results.asp?loc=archive/0... >. "Macular Degeneration: A New Approach to Treating the Dry Form" Ophthalmology Management Online <<a href="http://www.ophmanagement.com/archive_results.asp?loc=archive/9899110732am.html">http://www.ophmanagement.com/archive_results.asp?loc=archiv... >.
"National Study Finds Smoking, Hypertension, Antacid Use
Associated with Macular Degeneration" American Academy of Ophthalmology Online. <<a href="http://www.eyenet.org/aaoweb1/Newsroom/1155_32019.cfm">http://www.eyenet.org/aaoweb1/Newsroom/1155_32019.cfm>.
Roach, Linda. "Retina/Vitreous: Laser to Drusen Offers Hope for Dry AMD" EyeNet Magazine Online. <<a href="http://www.eyenet.org/eyenet_mag/retina.html">http://www.eyenet.org/eyenet_mag/retina.html>.