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Preoperative donor endothelial cell count does not affect the rate of dislocation in endothelial keratoplasty. The surgical technique is likely the most important factor that drives the dislocation rate, primary graft failure rate, and long-term endothelial survival, according to one surgeon.
Dr. Terry has experience with more than 500 cases of EK included in his institutional review board-approved prospective study. He performed the first EK in the United States in March 2000. Since then, variations of the surgical technique have been developed. As of spring 2007, Dr. Terry had performed about 275 cases of deep lamellar endothelial keratoplasty (DLEK), 32 cases of Descemet's stripping with endothelial keratoplasty (DSEK), and 225 cases of Descemet's stripping automated endothelial keratoplasty (DSAEK), including 80 cases in which pre-cut tissue was used.
Visual acuity results
"When we evaluated the approximately 100 DSAEK eyes that had 6 months of follow-up, the average VA was 20/37. Most importantly, if we eliminate the eyes with cystoid macular edema or age-related macular degeneration, 92% of the eyes that underwent DSAEK had 20/40 or better VA, 30% had 20/25 or better VA, and 12% had 20/20 or better VA, which is much better than we ever achieved with DLEK or penetrating keratoplasty," Dr. Terry said.
In addition to good VA results, the incidence of graft dislocation had decreased over time, he said.
"Initially, in our first 100 cases, we reported a 5% rate of dislocation with DLEK; however, as we performed more challenging cases with filtering tubes and IOL exchanges, the rate increased to 8% in 275 DLEK cases. The 32 cases of DSEK had a 6% rate (two cases) of dislocation. In the series of DSAEK cases, only three dislocations occurred among 223 cases, for a 1.3% dislocation rate," he said.
With those data in mind, Dr. Terry sought to determine which type of tissue to request from the eye bank.
"In the ideal world, the ideal tissue would be from a donor aged 25 years or younger, an endothelial cell count of 4,000 cells/mm2 or higher, and time from donor death to delivery to the operating room less than 1 hour while the tissue is still warm," he quipped.
Dr. Terry said that in the real world, however, he will accept tissue with an endothelial cell count ?2,000 cells/mm2 , a patient age <75 years, and a time since donor death 11 days.
"When we looked at the entire group of 532 cases for all EK procedures-the preoperative endothelial cell count in the 27 cases in which dislocation occurred compared with the 505 cases in which dislocation did not occur-preoperatively, there was no difference in the mean endothelial cell density," he said. "In fact, in eyes that did not dislocate, there was an endothelial cell count as low as 2,100 cells/mm2 , and in eyes in which dislocation occurred, the cell count was as high as 3,454 cells/mm2 . At least in this large series, dislocation did not depend on the preoperative endothelial cell count."