ENDOTHELIAL KERATOPLASTY

While Descemet’s membrane endothelial keratoplasty (DMEK) is a technically more difficult procedure, it provides better visual results with fewer problems than Descemet’s stripping endothelial keratoplasty (DSEK), so it is worth the extra effort, reports Yuri McKee MD. “The finding that DMEK reduces the rejection risk is the real game-changer in its favour, and now we are finding the lower rejection risk probably allows for a decrease in the steroid burden after DMEK with the potential for decreasing steroid-related complications,” he said. Dr McKee is in private practice at the Price Vision Group, Indianapolis, IN, where more than 1,100 DMEK cases have been performed since March 2008. Speaking at the 4th EuCornea Congress in Amsterdam, he reported findings from outcomes analyses in a series of eyes that had DMEK, DSEK and penetrating keratoplasty (PK). Data on vision outcomes came from follow-up to one year in a group of patients who underwent DMEK and DSEK in fellow eyes. Mean logMAR BSCVA was better in the DMEK eyes than after DSEK, 0.07 vs. 0.20. Moreover, 85 per cent of patients stated they preferred the vision in their DMEK eye due to better quality. Data on risk of transplant rejection were reported in a published study that included 141 DMEK eyes, 598 DSEK eyes and 30 PK eyes [Ophthalmology. 2012;119(3):536-40]. Based on Kaplan-Meier survival analysis and defining rejection as any amount of corneal oedema after initial clearing with any amount of inflammation, the two-year cumulative probability of rejection was less than one per cent for DMEK, 12 per cent for DSEK and 18 per cent for PK. “The DMEK eyes had a 15-fold lower risk of rejection than the DSEK eyes and a 20-fold lower risk than the PK group. Those differences were highly statistically significant and importantly, they were found in cohorts of patients that were operated on at a single centre, had similar indications for surgery, represented a similar racial mix and received the same steroid dosing regimen,” Dr McKee said. He added that there have been only nine rejection episodes among the more than 1,100 DMEK procedures performed in the past 5.5 years. Those events occurred between two weeks and four years after surgery, and in only one case was rejection associated with graft failure. Data on primary graft failures highlighted the learning curve with DMEK, showing that the cornea failed to clear in six of the first 80 cases and in four of the second 80. In contrast, there were five primary failures in the first 80 DSEK eyes, but only one in the next 80 cases. “The graft is more difficult to prepare, manipulate and attach when performing DMEK compared with DSEK. However, in more recent studies of DMEK, the graft preparation failure rate is only one per cent, and now there are eye banks preparing the DMEK graft,” Dr McKee said. Other data Dr McKee presented showed similar outcomes for DMEK and DSEK. Both had better long-term endothelial cell survival than PK. Based on follow-up of 3-5 years, DMEK and DSEK are associated with excellent mid- to long-term graft survival. DMEK graft survival rates were analysed using data from cases performed at the Price Vision Group between March 2008 and September 2010. Focusing on the 143 eyes with Fuchs' dystrophy, Dr McKee reported there were only three late failures, including an endothelial failure without rejection, an endothelial failure after rejection and a regraft for poor vision. In a DSEK cohort of 147 eyes with Fuchs' dystrophy, six late failures occurred during follow-up to five years, of which four were regrafts for poor vision. Two randomised studies have been undertaken to investigate whether the intensity of steroid treatment could be reduced after DMEK. In both studies, patients received prednisolone acetate four times daily for the first month and then are randomised to continue prednisolone acetate or to receive fluorometholone 0.1 per cent in one study or to loteprednol etabonate 0.5 per cent in the other trial. The same tapering regimen is used over the next 11 months in all steroid groups. Dr McKee reported that preliminary findings from the study comparing prednisolone acetate and fluorometholone, which enrolled 325 eyes, show no difference in rejection rates between the two groups. However, prednisolone acetate was associated with a significantly higher rate of IOP elevation than fluorometholone. “The risk of cataract from steroid treatment is less of a concern among DMEK patients because most are pseudophakic. However, we know that steroid use is a balancing act between avoiding rejection risk and IOP elevation,” Dr McKee said.

Tags: quality control