Cell loss plateaus earlier in certain keratoplasty cases

October 15, 2009

Endothelial keratoplasty procedures continue to evolve, and researchers have begun to accumulate enough data to compare outcomes from techniques considered new less than a decade ago with still newer ones.

Findings show that despite declining cell count, 95% of DLEK eyes remain clear past the 5-year visit. Further, graft replacement has not been necessary in patients with even longer follow-ups, said Mark A. Terry, MD, who presented the latest findings from his ongoing prospective study of EK procedures at the annual meeting of the Association for Research in Vision and Ophthalmology. Dr. Terry, director of corneal services, Devers Eye Institute, Portland, OR, was the first surgeon in the United States to perform any form of EK and has developed both the DLEK and DSAEK procedures.

He reported that the rate of endothelial cell loss, the key factor for the long-term success or failure of EK procedures, appears to plateau between 4 and 5 years after DLEK surgery. He added that shorter-term results of DSAEK cases are very encouraging and seem to show an early plateau of cell density at 6 to 24 months postoperatively.

Factors that contribute to late graft failure and endothelial cell loss in EK cases include surgical trauma at the initial surgery, graft dislocation and rebubbling, and graft rejection.

Dr. Terry reviewed these factors in a series of the first 36 DLEK cases he performed, in which he had used a 9-mm incision for insertion. The dislocation rate was 1/36 (2.8%), whereas the graft failure rate was 0. This compared well with his series of 500 DSAEK cases, performed by a group of five surgeons who used an identical technique with a 5-mm incision, he said. The dislocation rate was 9/500 (1.8%), and both the primary graft failure and pupillary block rates were 0.

"We have a very low (1.8%) dislocation rate and also minimal surgical trauma as evidenced by our primary graft failure rate of 0 in 500 initial DSAEK cases. Therefore, this EK series likely represents a best-case scenario in terms of long-term cell loss and graft survival," Dr. Terry said. "Graft survival and endothelial cell loss in a series by other surgeons that might have a higher dislocation rate and a higher rate of primary graft failure would likely fare worse in the long term than the results reported here with our series. Therefore, what I'm reporting in terms of long-term graft survival might not be applicable to other studies."

DSAEK cases

He said that some small cases series of DSAEK, a form of EK developed within the past several years, have reported a cell loss rate of 38% to 50%. Larger studies have shown a much lower rate of 25% to 35%, however, and a review of the first 285 cases performed by Dr. Terry's group found a cell loss rate of 30% at 6 months and 12 months and 31% at 24 months.

Similarly, he said that a recent editorial by Frank Price, MD, of Indianapolis, mentioned that the endothelial cell loss in more than 100 of his DSAEK cases was minimal between 2 and 3 years, following a similar percent cell loss in the first 6 months postoperatively.