Long-term Outcomes of Endothelial Keratoplasty Win Over Penetrating Keratoplasty

Christopher J. Rapuano, MD


January 17, 2017


I selected this study even though I commented on a similar graft registry study from France about 9 months ago. This study is much larger and more representative of the real world. The French study only had 1132 grafts, and only 20% of them were EKs. This Dutch study had about 5000 grafts, more than half of which were EKs. The French study looked primarily at graft survival, which is important, but the Dutch study also looked at visual acuity, refractive outcomes, and ECDs.

The French study demonstrated that the 1-year survival for EK was 60% and for PK was 91%. The current Dutch study looked at 2-year results and also found worse survival for EK (89%-95%) than PK (95%-97%), but the numbers were substantially closer to each other. Owing to the much larger database, the Dutch study was able to look at 5-year results, which showed very similar 5-year graft survival between EK and PK. However, the visual acuity and refractive outcomes were much better (and were achieved more quickly) in the EK eyes than PK eyes. The rapid improvement in vision, better visual acuities, and better and more stable refractive outcomes achieved with EK compared with PK are the primary reasons that surgeons have overwhelmingly transitioned to EK for endothelial disorders. In fact, several years ago, EK overtook PK as the most performed corneal transplant procedure in the United States.

Those of us who learned to perform EK around the time it was first introduced more than a decade ago were quite concerned about the damage we were causing to the endothelial cells with this new technique. Many surgeons were expecting these EKs to fail earlier than PKs for similar reasons. However, surgeons were generally willing to accept lower graft survival rates in their EKs because of the distinct advantages of more rapid and better visual outcomes.

Additional benefits included no "open-sky" time and much smaller wounds, decreasing the risk for traumatic wound rupture. An advantage many of us didn't expect was the lower graft rejection rate for EK compared with PK. Fortunately, with greater experience (after the learning curve) and longer-term follow-up, it is wonderful to learn that we no longer have a big difference in graft survival.

Some unanswered questions remain regarding EK and PK for endothelial disease. One is why the graft failure rates for both EK and PK are lower for PBK than FED. This was assumed by many of us to be from greater endothelial cell loss due to fewer "normal" remaining peripheral endothelial cells in PBK compared with FED. However, this study, which is the first of the big registry studies to systematically look at ECDs, did not show a difference in ECDs between FED and PBK over the 5-year period.

Needless to say, more research is needed to address this issue. I am hopeful that as we learn more about Descemet stripping EK results, the information can make the learning curve for Descemet membrane EK even faster.



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