The Importance of Corneal Endothelial Cell Survival After Endothelial Keratoplasty.

Abstract

The transition from penetrating keratoplasty to endothelial keratoplastyduring thepast 2decadeshasbeenadramatic improvement in the treatment of patientswith corneal endothelial disease. With the introduction of Descemet membrane endothelial keratoplasty (DMEK), we are approaching the goal of pure endothelial cell transplantation. In this issue of JAMAOphthalmology, Baydoun et al1 present endothelial cell data fromtheoriginalDMEKcohort.Asendothelial cell function is critical for corneal clarity, endothelial cell loss is important. Examination of decreasing endothelial cell density (ECD) over time after DMEK should help us to compare this techniquewith penetrating keratoplasty andDescemet stripping automated endothelial keratoplasty and to predict longterm corneal transplant survival. Post–penetratingkeratoplastyendothelial cell losshasbeen evaluated in the Cornea Donor Study (CDS) with the finding of a median cell density of 611 cells/mm2 and 76% cell loss at 10 years.2 Cell density less than 1700 cells/mm2 at 6 months predicted an increased risk of later transplant failure. Endothelial density is not, however, the whole story on corneal health, nor is it a perfect proxy for future failure. The critical threshold of 500 cells/mm2 referred to by Baydoun and colleagues has only tentative support. Graphs of post– penetrating keratoplastyECD in theCDSandother studies appear to showECDover time approaching an asymptote of 500 cells/mm2, possibly explained by transplant failure at lower counts and censoring from the data.2 However, 42 of 176 CDS patientswith clear grafts and endothelial data at 10 years had ECD less than 500 cells/mm2 and 71% of 49 clear grafts with ECD less than 500 cells/mm2 at 5 years still survived at 10 years.2,3The261cells/mm2–lowerpost-DMEKECDineyeswith bullouskeratopathy than in thosewithFuchsdystrophy in the study by Baydoun and colleagues correlated with better survival at 8 years for DMEK transplants in eyes with Fuchs dystrophy than in those with bullous keratopathy (97% vs 84%, respectively). Caution iswarranted in interpreting thesedata, as the number of cases is small at later times and the cases of bullous keratopathy are few. The better survival of eyes with Fuchsdystrophywas alsomarked in theCDS.3 The reasons for this difference are not known, but theymay emerge from further study of endothelial biology in both conditions. It is difficult to factor out most other influences potentially affectingDMEKsurvival. Thenumberof caseswithprior glaucoma surgery in the study by Baydoun and colleagues is Related article page 1277 Endothelial Survival After Descemet Membrane Endothelial Keratoplasty Original Investigation Research

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