AMD Risk and Aspirin Use
BY LEO SEMES, OD, FAAO
About a year ago, an increased risk relationship between aspirin use and age-related macular degeneration (AMD) was reported by the Beaver Dam Eye Study (Klein et al, 2012). The study follows a cohort of patients generally of European and Caucasian descent in the Midwest. The results suggest that 10 years of aspirin use may represent a small increased risk for neovascular AMD. However, shorter-term regular use of aspirin (<5 years) was not associated with either early, late, or neovascular AMD. Without looking closely at the results, it would be tempting to contemplate recommending that patients who have early signs of AMD consider discontinuing their aspirin regimen.
A Prescribed Aspirin Regimen
Aspirin is used for primary and secondary prevention of cardiovascular events (Siller-Matula, 2012). The benefit of aspirin in low-risk cases has been reported to be minimal to questionable (Berger, 2010). While its use is widespread, aspirin’s ophthalmic complications have been reported only sparsely (Black and Bensinger, 1982; Elgohary and Gormley 2005; Witmer and Cohen, 2012).
Can we connect subconjunctival, macular, or even vitreous hemorrhage as a consequence of aspirin use? These rare if significant complications along with the low likelihood of aspirin use complicating AMD suggest that we should not tamper with recommended aspirin use.
Two Recent Studies
Two recent epidemiological studies looked at hemorrhagic complications associated with aspirin use. One study specifically addressed the association of aspirin use and bleeding among diabetics compared with non-diabetics (De Berardis et al, 2012). This report examined the records of more than 1.4 million people. Because it was done in Italy, the dose was specified only as ≤300mg. The investigators looked specifically at major bleeding, defined as gastrointestinal bleeding requiring hospitalization and intracranial bleeding episodes. Interestingly, no ophthalmic events were reported. The study design did not mention that ophthalmic events were monitored. The study protocol was careful to account for a number of other confounding factors such as systemic medication use, smoking, and other lifestyle items.
Surprisingly, despite the fact that diabetes is a known vasculopathy, aspirin use produced only marginally greater risk of serious bleeding events among diabetics. The authors offered the explanation that an accelerated platelet turnover rate in diabetics could be responsible as a protective effect. The bottom line is that serious systemic bleeding risk is not potentiated by aspirin use.
The Blue Mountains Eye Study has been ongoing outside of Sydney, Australia, for years. Their cohort consists of a population that is similarly stable to that of the Beaver Dam Eye Study. In a recent report, this group concluded that regular aspirin use is associated with an increased risk of developing neovascular AMD in subjects followed over a 15-year period (Liew et al, 2013). Some perspective is in order here. Regular aspirin use was defined as once or more per week, with occasional use defined as less than once per week for the past year. In Australia most aspirin is 150mg as opposed to the 325mg dose available in the United States.
One interpretation of these seemingly conflicting results is that we should monitor our patients who are on aspirin therapy more closely for AMD complications. Recommending discontinuation of aspirin therapy is not consistently supported by large studies. Perhaps we can take solace in the fact that primary-care practitioners face some of the same conflicts (Kent and Shah, 2012). CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #209.
Dr. Semes is a professor of optometry at the UAB School of Optometry. He serves on the advisory board or speakers’ bureau of Alcon, Allergen, Optovue, Med Op, Merck, and B+L.