Today, I received a letter from a patient with a copy of an recent article linking aspirin use with blindness caused by age-related macular degeneration (AMD). She was understandably concerned and asked in her letter whether or not she should stop taking aspiring. I thought a post on the subject would be helpful for other patients who are similarly worried.
Macular degeneration is the leading cause of blindness for Americans older than 55 years old. The macula is the center most part of the retina responsible for the fine central vision. I always tell patients that the retina is like the camera film of the eye, but now with digital cameras, I’m not really sure what the equivalent would be! In any case, the retina is the inner lining of the eye and its cells record visual input and translate it to send back to the brain. The macula is a small pigmented area right in the in center of the retina.
And, here’s a depiction of the difference between a normal retina on the left side, dry AMD in the middle and wet AMD on the right.
There are 2 forms of macular degeneration – dry and wet. Most cases of macular degeneration (80-90%) are the dry form. In dry macular degeneration, there is an accumulation of “drusen” underneath the retina. These drusen, essentially represent the “garbage by products” of the retina and over time the deposits can interfere with the function of the macula. Though the dry form of macular degeneration is less severe and causes less vision loss, there is also no treatment for it.
The wet form of macular degeneration is caused by leakage of abnormal blood vessels underneath the retina (neovascularization). The blood vessels leak fluid and cause an elevation of the macula and disruption of central vision. Vision loss can be quite rapid and severe. However, for this form of macular degeneration, there are treatments available with anti-VEGF injections (Macugen, Avastin). The retina specialist will inject these medications directly into the eye and they help halt the formation of the abnormal, leaky blood vessels under the macula. Typically, these injections must be repeated every six weeks.
So, what’s the link between aspirin and macular degeneration? The article was published by the Journal of American Medical Association – Internal Medicine and it looked at roughly 2400 participants and followed them over a 15 year period. The patients were examined 4 times and asked to complete at baseline assessing aspirin use, cardiovascular disease status, and AMD risk factors. The authors found that regular low dose aspirin use is associated with a 2.5 fold increased risk of wet (but not dry) AMD. By the end of the study period, 24.5 percent of the study participants had developed “wet,” or neovascular, age-related macular degeneration. But researchers found that a greater proportion of regular aspirin users had the disease as they followed up throughout the years than the aspirin non-users. This study does not prove that aspirin causes macular degeneration. It simply shows there is an association between the two.
A related commentary in the same journal, points out flaws of the study, which undermine the results, and call for additional studies. They write, ” the strength of evidence is not sufficiently robust to be clinically directive.” Meaning, the evidence is not strong enough from this study to make changes in clinical care, further prospective, randomized studies are indicated. Previous studies investigating AMD and aspirin have been inconclusive.
Bottom line – physicians should take this study into account when prescribing aspirin for their patients for prevention of cardiovascular events. The benefits of initiating aspirin therapy (prevention of heart attacks or possibly cancer) must be weighed against the risks (development of AMD and bleeding), as with any treatment. Whether or not to start aspirin should be a discussion each patient has with their physician, now with additional information regarding AMD. Patients who use aspirin for pain control, may want to do so with caution, given this association.