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Spotting macular degeneration: Be watchful and start early

The potential of preventive strategies and early interventions to curb resulting vision loss puts this condition squarely in the sights of primary care physicians.

By Kathleen Phalen Tomaselli, amednews correspondent. Sept. 1, 2003.

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It's the difference between clear vision -- sharp contrasts and vivid lines -- and a world of shadows and faceless silhouettes. But it often slips past physicians' notice and rarely makes patients' lists of complaints, even though it can significantly undermine physical and mental well-being and quality of life.

The problem is macular degeneration. It affects as many as 25 million to 30 million people around the world and in the United States is the leading cause of vision loss and legal blindness in adults older than 60. As baby boomers age, incidence rates are expected to triple by 2025. Still, the epidemic numbers haven't pushed AMD onto primary care physicians' radar screen.

"This is an invisible problem for the family doctor," says Lylas G. Mogk, MD, founding director of the Visual Rehabilitation and Research Center of the Henry Ford Health System in Detroit and chair of the Vision Rehabilitation Committee of the American Academy of Ophthalmology. "Even people with advanced AMD will walk in the office and you won't know, because they often hide it."

But a growing body of research indicates that primary care and family physicians now can play an important role in helping delay or even halt the vision loss that the condition causes. The keys are prevention and early intervention techniques.

"Today there are a number of options," said Paul Sternberg, MD, chair of the Dept. of Ophthalmology and Visual Screening at Vanderbilt Medical Center and School of Medicine, Nashville, Tenn. "It's not like 10 years ago, when nothing could be done."

How the damage starts

There are differing theories about AMD's causes and progression, among them: a buildup of wastes caused by varying environmental and dietary factors; family history; a breakdown in circulation to the retina, untreated health problems such as hypertension; and smoking.

Bruce P. Rosenthal, OD, chief of Low Vision Programs at New York's Lighthouse International and chair of the Scientific Advisory Council of AMD Alliance International, says that as people age, certain cells in the macula deteriorate, but it is not clear why. He describes one theory this way: "As light enters the eye, it causes chemical reactions that activate oxygen, a process known as oxidation or rusting," he says. "The [retinal pigment epithelium] cells are being destroyed, and the resulting debris buildup causes damage to vision."

The damage, in turn, poses challenges for doctors, patients and families. Because peripheral vision generally is unaffected, family members often think the patient is faking, seeing what he or she wants to see. Sometimes, because the patient is unable to distinguish faces, he or she is labeled with early dementia. And, says Dr. Mogk, AMD puts patients at risk for medication mix-ups, poor nutrition, falls and depression. "There is more depression with this than any other disease, including cancer," says Dr. Mogk. "There is a grief reaction. This is a tremendous loss."

Of the two primary types of AMD, wet and dry, about 85% to 90% have dry AMD, the less severe, slower-progressing form. About 10% to 15% of these cases, though, advance to the more severe wet AMD, called choroidal neovascularization. Wet AMD accounts for 90% of the blindness caused by macular degeneration. It is characterized by the formation of fragile new blood vessels that leak blood and fluid under the macula.

There is no reversing and no curing AMD. But recent advances point to prevention, early intervention and primary care involvement to slow its progression.

"The main thing that primary care doctors can do is recognize that macular degeneration is a condition that starts without symptoms," says Dr. Sternberg. "By the time patients suffer vision loss, they are way down the road with the disease. So even if older patients have great vision, they need an eye exam."

There are also new preventive steps. For instance, the National Eye Institute's 10-year Age-Related Eye Disease Study, known as AREDS, found that a high-dose combination of antioxidants, vitamins C and E, betacarotene and zinc lowered the risk for those at highest risk for developing advanced AMD by 25% and reduced the risk of vision loss caused by advanced AMD by 19%. "Even some ophthalmologists aren't aware of this," says Emily Chew, MD, deputy director of NEI's Division of Epidemiology and Clinical Research and an AREDS principal investigator. "This study shows there is an effective form of prevention with vitamins."

And scientists at University of Michigan's Kellogg Eye Center, Ann Arbor, have linked gene mutations on the X chromosome to degeneration of the macula. In a study published in the August Investigative Ophthalmology & Visual Science, researchers say they have found a mutation (Tyr141Cys) in a gene called RDS that is responsible for an inherited eye disease that mimics macular degeneration. Kellogg scientist Radha Ayyagari, PhD, and other researchers suspect that some individuals with AMD also might harbor the RDS mutation.

Wasting

Drusen, the hard, tiny yellow spots commonly found in aging eyes, are much like age spots on skin. These lipid and calcium deposits found under the retina are often harmless. But they also can be precursors to AMD. An increase in the number or size of drusen or a change in their consistency often signal the disease. Soft drusen, nearly twice the size of hard, are thought to clog up the macula's system of nourishment and waste removal.

Because drusen cannot be seen without dilating the eye, Dr. Sternberg says family doctors need to refer all older patients for annual eye exams. "As the retina ages, we get drusen," says Dr. Sternberg. "With the eye we have the advantage that we can examine the tissue, and we're certain that some drusen lead to vision loss."

Smoking is the only proven modifiable risk factor, but there are other factors that should raise the suspicion index regarding certain patients. These include a family history of macular degeneration; fair skin, blond hair or blue eyes; farsightedness; high blood pressure; high cholesterol; diabetes; cardiovascular problems; and excessive exposure to ultraviolet light. "Seven to 8 million people are at moderate risk for AMD," says Dr. Chew. "With early detection, we can intervene."

If spotted sooner, patients in these categories could modify lifestyle factors, begin taking antioxidants and be monitored for vision changes.

Meanwhile, photodynamic therapy offers new hope for patients once diagnosed. "It's the first new treatment in 30 years," says Dr. Rosenthal.

Nourishing

The AREDS study is the first to clinically prove that antioxidants and zinc slow the progression of AMD. Antioxidants work to neutralize free radicals before they react with and harm other cells, says Dr. Rosenthal. "Free radicals are waste products of other working cells in our bodies; they are what cause unwanted oxidation and, if unchecked, invade and injure healthy cells," he says. "We are exposed to free radicals through a range of environmental factors, from dietary fats and food additives to car exhaust and tobacco. Even breathing can create free radicals in the body."

The nutrients evaluated by the AREDS researchers contained 500 mg of vitamin C, 400 IUs of vitamin E, 15 mg of betacarotene, 80 mg of zinc as zinc oxide, and 2 mg of copper as cupric oxide. The vitamin and mineral formulation, created by Bausch & Lomb and marketed as Ocuvite PreserVision, is an oral preparation and costs about $17. "This was remarkable," says Dr. Sternberg, who was involved in the ARED study while at Emory Eye Center. "It demonstrated that a nutritional supplement reduced vision loss from macular degeneration. This study actually demonstrated a difference."

Although observational data and small studies also point to the benefits of diets rich in green leafy vegetables, it would be hard to achieve such high levels from diet alone. "You'd have to eat a roomful of wheat germ," says Dr. Chew.

Still, Dr. Rosenthal and others say dietary changes are important. Primary care doctors can encourage patients to eat foods high in lutein and zeaxanthin, carotenoid nutrients that researchers believe protect the macula. "Lutein is very protective against UV and blue light," says Dr. Rosenthal. Lutein-rich foods include spinach, kale, collard greens, corn, kiwi, pumpkin, zucchini squash, yellow squash, green peas, green bell peppers and celery. Patients should also eliminate vegetable fats, artificial fats and trans fats from their diets. "Trans fats found in burgers and fries seem to be implicated in negative blood vessel change," says Dr. Rosenthal. And Dr. Mogk says increasing the intake of omega-3 fatty acids, found in fish, fish oil and flax seed oil, for example, is important to eye health. "I tell my patients to take one to two tablespoons of flax seed oil every day."

Living

Blurred, indecipherable images are common to patients with AMD, as are phantom visions such as purple flowers on khaki pants or little girls in white dresses playing in the yard. Known as Charles Bonnet syndrome, more than 10% of patients see such nonexistent images.

"When the retinal cells become impaired and no longer able to receive and relay visual images to the brain, the system begins firing off images on its own," says Dr. Mogk. "It's like watching a silent movie. The patients do not interact with the visions."

According to Dr. Mogk, many doctors are not familiar with the syndrome, and patients are sometimes referred for psychiatric evaluation.

For many patients, AMD represents a serious loss. Some experience mild depression, but for many the grief is so profound that a prolonged period of depression follows. Primary care doctors can help patients with antidepressants, counseling or support groups and referral to a low-vision specialist. "We work with patients so they can continue with life activities," says Dr. Rosenthal. For instance, about 99.9% of patients with AMD retain peripheral vision, and low-vision specialists like Dr. Rosenthal help them maximize what remains by prescribing devices or vision rehabilitation.

"It's important for the family doctor to recognize the people at risk for [AMD] to minimize its development," says Dr. Mogk. "And it's important for them to know that there are tools that allow almost everyone to still see, read and keep functioning."

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