Eyeworld

EW CORNEA 28 April 2015 by Michelle Dalton EyeWorld Contributing Writer Shifting preferences in corneal transplantation continued on page 30 Device focus Anterior segment OCT showing cross section of corneas after DALK with zig-zag incisions. Zig-zag incisions provide for stronger wounds due to increased surface area of wounds that are not in the lamellar planes of the cornea, as well as provide for smooth contours of the anterior corneal surface even when donor and recipient corneas are of different thicknesses. Source: Francis Price, MD Postoperative DMEK eye looks like a normal eye without the typical scarring or edge reflections seen with either PK or DSAEK. The femtosecond laser and newer surgical techniques are changing how corneal surgeons perform keratoplasty P enetrating keratoplasty (PK) used to be the go- to procedure for all cor- neal diseases, whether stromal, endothelial, or epithelial, but in the last 15 years or so surgeons have transitioned to anatomic-targeted procedures. Two of the more commonly performed posterior procedures are Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descem- et's membrane endothelial kerato- plasty (DMEK), designed to replace damaged endothelium. The DMEK technique involves selective trans- plantation of Descemet's membrane through a self-sealing 2.8-mm or smaller clear corneal incision. Even during its introductory stages where surgeons admitted large learning curves, the visual rehabilitation was quick, and within 3 months, more than 90% of patients were already seeing 20/40 or better, said Francis W. Price Jr., MD, Price Vision Institute, Indianapolis. But PK has not been aban- doned altogether. In today's PK, the transition to femtosecond lasers to replace the trephine is preferred in most cases, said Peter S. Hersh, MD, in practice at the Cornea and Laser Eye Institute, Hersh Vision Group, Teaneck, N.J. DMEK, DSAEK At this point, Dr. Price said only 5% to 10% of his EK cases are DSAEK, and most are DMEK. He now reserves DSAEK for cases "that are re- ally compromised and complicated," including patients with an artificial iris implant or a large iris defect "where the donor could go into the posterior chamber or into the vitre- ous." Patients who have an anterior chamber lens or those who have undergone pars plana vitrectomy can also be problematic, as the vitrectomy has created empty space, making it difficult to shallow the anterior chamber, Dr. Price said. There are several techniques for performing DMEK, but "in one form or another, you're using the iris as a platform to unfold the donor tissue," Dr. Price said. "When you uncurl the donor, it will curl back up unless you shallow the anterior chamber to hold it open," he said. Patients with previous glauco- ma filtering surgery pose another concern—a low pressure (anything under 9 mm Hg, Dr. Price said) can allow the donor to detach when the eye is rubbed or even just closed with hard squeezing. During the procedure, when surgeons place air in the anterior chamber, previous filtration surgery may make it more difficult for the air to "stay put" as long as needed (a few days for DMEK and 10–15 minutes for DSAEK, Dr. Price said.). "Those are cases where DSAEK may be a better option than DMEK," he said. "It's something we're trying to analyze and work out." The key to a successful DMEK or DSAEK remains the surgeon—there's no difference in necessary instru- mentation between a complicated case and a straightforward case. "You just manipulate the graft different- ly," Dr. Price said. In DSAEK, Dr. Price tends to use 9 mm grafts, while he prefers 8 mm grafts for routine DMEK. Visual outcomes post-DSAEK are about 20/30 or 20/40, Dr. Price said, and some patients will still be un- happy with that visual acuity. Using DMEK, most patients are 20/15 to 20/20, he said. DMEK not only pro- duces better visual outcomes, there is a much lower rate of rejection when compared to PK. "That's been the game chang- er," he said. "The bottom line is that endothelial keratoplasty has revolutionized corneal transplants. It's absolutely amazing what we're seeing." Femtosecond or manual trephination PKs? The femtosecond laser is useful for 3 things, Dr. Hersh said. "It's good for penetrating keratoplasty, it's good for preparation of the donor

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