EyeWorld Asia-Pacific September 2018 Issue

by Maxine Lipner EyeWorld Senior Contributing Writer Post-cataract CME under examination Considering possible connection to medications I s there an association be- tween postoperative topical prostaglandin analog (PGA) or topical beta blocker use and the incidence of pseudopha- kic cystoid macular edema (CME)? This is what a study 1 published in the Journal of Glaucoma looked at. Initially investigators honed in on prostaglandin analog drops alone. “Ever since the prostaglan- din analog drops came out in the late 1990s, there has been discus- sion on whether use of prostaglan- din analogs in patients who have had cataract surgery increases the risk of developing CME,” accord- ing to Frederick Mikelberg, MD, professor, Department of Ophthalmology and Visual Scienc- es, University of British Columbia. Investigators decided it might be interesting to take a closer look at this. “Ideally we would do a prospective randomized trial but that’s not going to happen because this is a relatively low incidence disease,” Dr. Mikelberg said. They decided to work with a large administrative database and look for associations. Using a PharMetrics Plus database of 150 million patients, investigators looked for those who had developed postoperative CME. “There were 508 patients who fit that criteria,” Dr. Mikelberg said. They then selected 5080 individu- als from the database who had undergone cataract surgery but not developed postoperative CME to serve as controls. In addition to considering the prostaglandins, investigators designed the study to look at a couple of other medications that they thought would not interact to use on a control basis, Dr. Mikel- berg explained. “For example, we always throw in a systemic medi- cation that there’s no way could have a relationship to CME,” he said. In this case, the oral medi- cine ranitidine was used, as well as beta blocker eye drops also not suspected of being related to CME occurrence. “We included that medication because we thought it would be a useful negative con- trol,” Dr. Mikelberg said. Investigators were surprised to find that not only were the pros- taglandins significantly associated with an increased risk of develop- ing postoperative CME, but also that the beta blockers were an equally powerful risk factor here. Equivalent risk Investigators showed that the relative risk ratio with the beta blocker was 2.64 and with the prostaglandin analog was 1.86. “That might suggest that the beta blocker is even worse, however, we then compared the two to each other and found that the differ- ence between the 2.64 and the 1.86 was not statistically signifi- cant,” Dr. Mikelberg said. The fact that both of the drugs showed a relationship meant that investigators had to broaden their initial thinking. “If it was only the prostaglandins, we would hypothesize it’s some mechanism that prostaglandins are known to have,” Dr. Mikelberg said. “But it wasn’t. It was both the prostaglan- dins and the beta blockers.” There are several possibilities to explain what might be occur- ring, he continued. “One hypoth- esis is patients are put on these medications because they have elevated IOP with or without glau- coma,” he said. “Maybe it’s the diagnosis of glaucoma that puts these patients at increased risk.” Another hypothesis is that patients are put on this medica- tion because of a complication in the surgery. “A patient may have elevated IOP in the context of cataract surgery if the cataract surgery was complicated.” When there are complications with “ …the use of a beta-blocker or prostaglandin analog in the context of a patient who has had cataract surgery somewhat increases the risk of developing CME. ” - Frederick Mikelberg, MD 30 EWAP CATARACT/IOL September 2018