Eyeworld

EW FEATURE 46 Corneal lamellar surgical procedures April 2015 by Rich Daly EyeWorld Contributing Writer 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 membrane from the overlying tissue to help en- sure no stromal tissue is left behind. Although some surgeons use blunt cannulas to create the big bubble, Dr. Anwar prefers a 27 g hypoder- mic disposable needle. If he fails to achieve the big bubble, Dr. Anwar falls back on a manual technique to complete the case by near full thickness resection using fluid and air stromal emphysema technique. Dr. Price urged keeping the nee- dle close to Descemet's membrane and close to the central cornea when injecting to create the big bubble. "Most of us now use a blunt needle to reduce the chance of perforating Descemet's as you are advancing toward the center, espe- cially in a thin cornea," Dr. Price said. "These needles either have a hole that points down and the tip is blunt or is a beveled needle, but it is all blunt so you can advance it and inject air." A key point is to begin in- jecting a small amount of air—1 cc—because too much expansion too quickly can break Descemet's membrane. "When you are doing one of these big bubble preparations the bubble only goes out to 7–8 mm and very often there is an annulus there that stops it," Dr. Price said. "If you keep pressing hard with air 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, MD, Price Vision Group, 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 as- sociate 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 pa- tient'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 pro- tein formation in wound healing. The visual results that are reported between DALK—especial- ly when the big bubble technique is used—and PK are essentially the same, Dr. Price said. 1 However, DALK's visual results depend on re- moval 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 endo- thelial cell density within 6 months after DALK, while PK patients have shown longer-term loss. A shorter healing time, fewer postop compli- cations, and the ability to use donor tissue that may not be suitable for full-thickness grafts are all advantag- es of DALK. Surgical pearls Mohammad Anwar, MD, chief of the cornea unit, Magrabi Eye Hospital, Dubai, who prefers DALK for keratoplasty in diseased corneas DALK refinement may change its appeal Monthly Pulse Keeping a Pulse on Ophthalmology T he topic of this Monthly Pulse survey was "Corneal lamellar surgical procedures." We asked what you would recommend for a 65-year-old pseudophakic female patient who complains of glare from corneal guttae. The majority said DSAEK (Descemet's stripping automated endothelial keratoplasty); DMEK (Descemet's membrane endothelial keratoplasty) was the second most popular answer. For a 74-year-old female patient with a tube and pseudophakic bullous keratopathy, most respondents would recommend DSAEK. In the case of a 22-year-old male patient with keratoconus, average K readings of 75 D, and contact lens intolerance, most respondents would recommend DALK (deep anterior lamellar keratoplasty). Finally, for a 55-year-old male patient with keratoconus, a dense central corneal scar after an episode of hydrops, and contact lens intolerance, a large majority would recommend PK (penetrating keratoplasty). 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 func- tioning endothelium with PK's 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.

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