Incidence and Risk Factors of Intraocular Pressure Peaks in DMEK Surgery: A Comparison of Iridectomy and Iridotomy

Purpose After Descemet Membrane Endothelial Keratoplasty (DMEK), the air-gas compound in the anterior chamber can lead to a postoperative increase in intraocular pressure (IOP) up to pupillary block. YAG laser iridotomy (IO) or surgical iridectomy (IE) is performed to prevent these painful and sight-threatening elevations. We aimed to compare the safety profiles of the two procedures.Methods We included a total of n = 196 eyes of N = 178 patients (55.6% female and 44.4% male) who underwent DMEK. Of these, 124 eyes received intraoperatively an IE (63.3%, group IE) and 72 an IO one day before the surgery (36.7%, group IO). A procedural imbalance between both groups has to be noted, as phakic patients often underwent IO and the pseudophakic ones always underwent IE. The primary endpoint was the incidence of elevated IOP. Secondary endpoints were the clinical outcome (measured by endothelial cell count (ECC), visual acuity (VA), central corneal thickness (CCT)) and risk factors for pressure elevation.Results Group IO showed a significantly higher incidence of postoperative IOP values above 50 mmHg (p = .021), a higher absolute IOP immediately after surgery compared to group IE (p = .004; ω2 = .04) and a greater immediate IOP difference from preoperative to postoperative (p = .011, ω2 = .03). This difference resolved after 6 weeks and VA did not differ significantly between the groups. In pseudophakic eyes, a deeper anterior chamber depth (ACD) was associated with smaller immediate IOP difference (p = .026; ω2 = .06).Conclusions This study showed that preoperative laser IO might be an alternative to surgical IE, but sufficient postoperative pressure control and appropriate preoperative counseling are crucial as laser iridotomy is associated with a higher risk of peak pressure values > 50 mmHg and immediate pressure differences.