Ask the Doctors – What causes wet macular degeneration?
Dear Doctor: I was recently diagnosed with wet macular degeneration and am now receiving periodic injections for the disease. My question is: What causes it? Are there any risk factors, such as drugs or diet?
Age-related macular degeneration (AMD) is the leading cause of adult blindness in industrialized countries. AMD causes damage to the central portion of the retina, leading to a loss of central (foveal) vision. Central vision is necessary to see those visual details that allow people to read, drive, watch TV and perform many of the activities of daily living.
As for wet AMD, it’s caused by the growth of abnormal blood vessels behind the retina. These blood vessels leak, causing both fluid and blood to pool behind the retina. I regret to say that, without treatment, the prognosis is not good. The condition can lead to rapid vision loss, causing blindness within months or even weeks. While wet AMD accounts for only 10 to 15 percent of cases of AMD, it accounts for 80 percent of the blindness caused by AMD.
The biggest risk factor for both types of AMD is age, with people age 55-64 having a 0.2 percent risk of developing AMD, and those older than 84 having a 13.1 percent risk. Smoking cigarettes increases the risk of developing AMD by a factor of two to four, and the risk persists many years after stopping smoking. It also causes AMD to progress faster. Other risk factors: Having a family history of early-onset or severe AMD and having had a prior stroke or prior heart attack. There may be an association between AMD and aspirin or blood pressure medications (especially beta-blockers and nitroglycerin), but as of now no causality has been defined. Heavy alcohol consumption (more than 3 drinks per day) has been associated with early-onset AMD, but not with late-onset AMD.
In regards to diet, one study followed the dietary habits of 2,525 patients with age-related eye disease. Those who adhered to a Mediterranean diet had a 26 percent reduced risk of developing advanced, severe macular degeneration. Mediterranean diets are high in nuts, fish, vegetables, fruits and whole grains and low in red meat, processed meats and saturated fats. Also, antioxidant combinations that include vitamin C and vitamin E, as well as supplements of lutein with zinc, have been linked to a decreased risk in progression of AMD. So it is possible that deficiencies in these substances may increase the risk of AMD.
People who want to decrease their risk factors for AMD should stop, or not start, smoking; should avoid heavy alcohol use; and if their diet is high in saturated fat, should consider a switch to more of a Mediterranean diet.
Robert Ashley, MD, is an internist and assistant professor of medicine at the University of California, Los Angeles.
Ask the Doctors is a syndicated column first published by UExpress syndicate.