EyeWorld Asia-Pacific June 2015 Issue

Corneal lamellar surgical procedures June 2015 34 EWAP SECONDARY FEATURE DALK refinement may change its appeal by Rich Daly EyeWorld Contributing Writer AT A GLANCE • ALK and PK continue to show generally similar clinical outcomes. • DALK techniques can further improve visual outcomes and reduce the incidence of complications. • If Descemet’s membrane is broken, a number of options have emerged to address the issue. I mprovements in techniques continue to widen the appeal of deep anterior lamellar keratoplasty (DALK). The surgical procedure for removing the corneal stroma down to Descemet’s membrane has evolved since its earliest version in the 1950s. As the procedure has changed, it is increasingly seen as able to provide comparable visual outcomes without some of the safety risks of penetrating keratoplasty (PK). The latest improvements in techniques may further popularize the procedure once thought of as tedious and requiring extensive experience. Advantages/disadvantages Among the chief advantages of DALK over PK in patients with healthy corneal endothelium is a lower endothelial rejection rate. Instead of treating corneal disease in the presence of normally functioning endothelium with PK’s full-thickness corneal graft, DALK lessens some risks by preserving the recipient Descemet’s membrane and endothelium. “The biggest advantage of DALK is that it minimizes the risk of long- term rejection,” said Francis W. Price, Jr., MD, Price Vision Group, Patient post-PK who had PRK Same patient Source (all): Francis W. Price, Jr., MD Indianapolis. “However, it doesn’t eliminate it.” Dr. Price has seen rejection episodes at the stroma, usually while sutures are in place, but other rejection has occurred up to 3 years postop. He views stroma rejection in DALK as a real issue, and has about a 5% rejection in those procedures. In comparison, Dr. Price’s Descemet’s membrane endothelial keratoplasty (DMEK) cases have a less than 1% rejection rate within 2 years postop. Stromal and epithelial rejections are less significant compared to corneal endothelial graft rejection, said Thomas John, MD , clinical associate professor, Loyola University, Chicago. Stromal rejection rates in DALK range from 2% to 12% among published studies. “Rejection can be controlled with steroids, and the frequency of the steroids should match the intensity of the rejection episode,” Dr. John said. Dr. John underscored the need for appropriate short-term steroid use with close monitoring of IOP until full resolution to avoid stromal haze that can interfere with the patient’s final visual outcome. Dr. Price noted that the length of steroid use in DALK patients remains open to debate, but he said that shortened use might allow for stronger wound healing because steroids inhibit protein formation in wound healing. The visual results that are reported between DALK—especially when the big bubble technique is used—and PK are essentially the same, Dr. Price said. 1 However, DALK’s visual results depend on removal of almost all of the recipient stromal tissue to eliminate scarring in the interface. “This interface has to clear to get the optimal vision,” Dr. John said. “The wait for clearance of the interface varies from patient to patient, but it’s usually going to take some time for the interface to clear.” That is a disadvantage from PK because there are no interface issues with PK, Dr. John said. Other advantages of DALK include evidence of stabilized endothelial cell density within 6 months after DALK, while PK patients have shown longer-term loss. A shorter healing time, fewer postop complications, and the ability to use donor tissue that may not be suitable for full-thickness grafts are all advantages of DALK. Surgical pearls Mohammad Anwar, MD , chief of the cornea unit, Magrabi Eye Hospital, Dubai, who prefers DALK for keratoplasty in diseased corneas with healthy endothelium, aims to debulk the cornea by about 50% before creating the big bubble. The big bubble technique detaches the recipient’s Descemet’s