LAUSR

Dear Editor, Immune reactions (IR) are the main reason for graft failure after keratoplasty. The risk of developing an IR after “Descemet membrane endothelial keratoplasty” (DMEK) is considerably low [1, 2], and we have previously shown that the IR rates after DMEK are about 1% at 1 and 2% at 4 years postoperatively [3, 4]. Factors/events that increase the IR risk after DMEK are largely unknown, although it is accepted that too early reduction/discontinuation of postoperative corticosteroids increases the risk [3, 5]. Interestingly, Monnereau and coworkers have demonstrated that characteristic endothelial cell changes can already be observed several months before an IR becomes clinically apparent [6], indicating that an IR may not be an acute event, but rather a slow-onset, protracted immunological response. Based on this, one could speculate that IRs might even be triggered by intraor early postoperative events. Another early, common complication after DMEK is cystoid macular edema (CME), with an incidence of about 10% [7]. Early intensified topical corticosteroids with hourly application in the first postoperative week can significantly reduce the risk for CME [8]. However, no study has so far investigated whether IR rates after DMEK can also be reduced by early intensified application of corticosteroids. Therefore, we aimed to analyze a potential protective effect of hourly corticosteroids in the first postoperative week on the incidence of IR episodes in a large DMEK cohort with a 2-year follow-up. All eyes that underwent DMEK surgery between July 2011 and December 2018 at the Department of Ophthalmology, University of Cologne, Germany, were screened for eligibility for this retrospective interventional case series. Until the 31st of March 2014, the first week’s postoperative standard therapy in our center was prednisolone acetate 1% applied 5 × daily (group 1). Since the 1st of April 2014, the first week’s postoperative standard therapy was changed to prednisolone acetate 1% applied hourly for 1 week (as we had shown that this regimen minimizes the risk for postoperative CME), which was then tapered to 5 × daily (group Key messages