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Descemet-stripping automated endothelial keratoplasty procedure seems to be supplanting penetrating keratoplasty as the standard of care for vision loss from corneal edema.
Chicago-Descemet-stripping automated endothelial keratoplasty (DSEK) seems to be supplanting penetrating keratoplasty (PK) as the standard of care for vision loss from corneal edema. PK procedures have declined by more than 40% in the past 5 years, whereas DSEK procedures have increased 13-fold in the same period.
However, despite excellent early visual outcomes, DSEK's preferred status may be in jeopardy due to accelerated endothelial cell loss, said Shahzad I. Mian, MD, who discussed PK and DSEK in a cornea subspecialty day presentation at the annual meeting of the American Academy of Ophthalmology (AAO).
He explained that clinicians have long-term experience with PK, and that the Cornea Donor Study produced solid prospective data for acute endothelial cell injury as well as long-term endothelial cell loss. In contrast, the data so far on DSEK indicate greater rates of acute endothelial cell injury and an unknown rate of endothelial cell loss that could lead to greater long-term graft failure.
A prospective, randomized, multicenter trial is necessary to compare the outcomes of the two procedures, said Dr. Mian, associate professor, ophthalmology and visual sciences, Kellogg Eye Center, University of Michigan, Ann Arbor.
Traditionally, PK has been assessed by graft survival, and by this metric has had excellent outcomes. The recent Cornea Donor Study, which looked at 1,100 patients prospectively, showed an 86% graft survival rate at 5 years.
"This study is powerful because it's prospective and included [more than] 100 surgeons," he said.
PK has well-known limitations, however, such as prolonged visual rehabilitation, graft rejection, and suture-related complications, and these limitations led first to the development of descemetorhexis in 2004, then to DSEK.
Advantages of DSEK include a small incision, fewer sutures, reduced astigmatism, greater tectonic stability, and faster recovery of vision.
Several studies have indicated that the complication rates for DSEK and PK are comparable, except for graft detachment or repositioning, which can only occur with endothelial keratoplasty, Dr. Mian noted.
Disadvantages associated with DSEK include posterior graft dislocation and increased endothelial injury with primary graft failure. The overall incidence of posterior graft rejection varies widely. A white paper from the AAO reported rates ranging from 0% to 82% with a mean rate of 14.5%.
Long-term data lacking
But due to the relatively recent development of endothelial keratoplasty procedures, long-term outcomes data are unavailable.
"There are factors that are just not known yet," Dr. Mian said. "There's increased primary graft failure, but we don't know about what's going to happen in the long term regarding graft survival."
The long learning curve for performing DSEK procedures, which even experienced corneal transplant surgeons face, is a component of the highly variable graft rejection rates, Dr. Mian said. The failure fate can be decreased with appropriate case selection, avoiding those involving eyes with glaucoma, tube shunts, or open anterior chambers.
Endothelial injury can occur for many reasons, including preoperative risk factors such as glaucoma, and a host of intraoperative factors, including air bubbles, incision size, IOL exchange, precut versus surgeon-cut grafts, graft size, surgeon experience, the combined endothelial keratoplasty/cataract/IOL procedure, and insertion technique.
The use of precut rather than surgeon-cut tissue may be an advantage, he continued, citing a study with 24-month follow-up showing that the endothelial cell loss rate was greater with surgeon-cut grafts.
Dr. Mian suggested that surgeons also should evaluate DSEK from a financial perspective.
"Precut tissue is not cheap," Dr. Mian said. "We pay extra money for this as a health-care system, and when we have to repeat the surgery because of graft failure it will further increase our cost."
Shahzad I. Mian, MD
Dr. Mian does not have any financial disclosures.