PK eliminates interface

Roger F. Steinert

Penetrating keratoplasty replaces all layers of the cornea. This eliminates optical degradation from alterations in the surface and stroma that accompany epithelial and stromal edema. The successfully healed PK has normal thickness and avoids the creation of an interface, as lamellar techniques require, that frequently degrades both high-contrast visual acuity and the quality of vision. However, PK also requires a 360° incision that heals slowly and often introduces both astigmatism and higher-order aberrations. The goal of femtosecond laser incisions in PK is to improve the integrity of the incision and the postop optics.

Roger F. Steinert, MD, is an OSN Cornea/External Disease Board Member.

EK offers rapid visual recovery, stable refraction

Edward J. Holland

In 2007, 37% of all corneal transplants and 85% of grafts performed for endothelial disease in the U.S. were endothelial keratoplasty. Advantages of EK over PK include faster visual rehabilitation and refractive stability, decreased surgically induced astigmatism, fewer sutures yielding fewer suture-related complications and a smoother anterior corneal surface, better tectonic stability, avoidance of open-sky, less irregular astigmatism and faster operating times.

As for outcomes, we recently reported that with thin tissue (less than 131 µm), 100% of patients had best corrected visual acuity of 20/25 or better and 71% obtained 20/20 vision after DSEK. A review of 34 articles found a mean postoperative change in refractive cylinder of 0.11 D and an average graft survival of 94% at 1 year after DSEK.

However, EK is not exempt from complications. Donor dislocation is the most common complication, occurring in 14.5% of cases. Also, endothelial cell loss at 1 year (42%) is substantially higher than in PK. Average rejection rate for DSEK has been reported at 10%. Glaucoma after DSEK can occur either by pupil-block secondary to the air bubble in the postoperative period or by steroid-induced glaucoma.

Based on personal experience and overwhelming support from the peer-review literature, the advantages of endothelial keratoplasty significantly outweigh the disadvantages, and we strongly advocate endothelial keratoplasty in all cases of isolated endothelial disease.

Edward J. Holland, MD, is an OSN Cornea/External Disease Board Member.

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