Eyeworld

EW CORNEA 60 May 2017 Surgeons update key techniques to provide the best results for penetrating keratoplasty A mid the spread of corneal surgical options, pene- trating keratoplasty (PK) remains an important option for some patients. Don't forget your PKs By Rich Daly EyeWorld Contributing Writer O ver the last 15 years, with improved instrumentation and new tech- niques, we have seen the alphabet soup of corneal transplant procedures grow to allow for the targeted replacement of the specific abnormal layer of the cornea. Procedures to correct for an endothelial layer problem include Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descemet's membrane endothelial keratoplasty (DMEK). Deep anterior lamellar keratoplasty (DALK) allows for removal of any anterior pathology where the patient's corneal endothelium is healthy. However, do not forget that the original full thickness cornea transplant— penetrating keratoplasty (PK)—is still an important option for some patients. Cornea surgeons still need to be able to perform PKs effectively and safely. The most recent 2016 Eye Bank Association of America statistical report had data showing that 18,579 PKs, 1,232 DALKs, and 28,327 EKs were performed in the United States last year. While the numbers of PKs have been decreasing steadily since 2005, there is still a significant number being performed. Given that the technique for PK inherently involves an "open sky" with the potential devastating risk of suprachoroidal hemorrhage, surgeons should be familiar with techniques to optimize the patient's outcome. In this month's Cornea editor's corner of the world column, David D. Verdier MD, and Woodford S. Van Meter, MD, share their expertise on what the indications are for PK, how to avoid and manage intraoperative adverse events, how to approach phakic vs. pseudophakic eyes, how to decide on the graft size, and how to best manage the patient postoperatively. Clara C. Chan, MD, FRCSC, FACS, Cornea editor Patient with severe corneal scarring from Acanthamoeba infection, with bilateral blindness from Acanthomoeba in both eyes. But the best results require use of proven techniques. David D. Verdier, MD, Verdier Eye Center, and clinical professor, Michigan State University College of Human Medicine, both in Grand Rapids, said PK was the gold stan- dard for most keratoplasties until the past 15 years, when PK was over- taken by lamellar procedures (De- scemet's membrane endothelial keratoplasty, Descemet's stripping automated endothelial keratoplasty, and deep anterior lamellar kera- toplasty). Now, those procedures, which replace the damaged layers of the cornea and leave the heathy layers intact, comprise up to 95% of cases. But PK is still indicated for cor- neal diseases or scarring that involve both stromal and endothelial layers. Possible PK indications include deep or full depth ulcers, immu- nologic melts, large perforations, herpes simplex or zoster keratopathy with endothelial involvement, and keratoconus with compromised De- scemet's/endothelium from hydrops sequelae, Dr. Verdier said. The typical PK patient for Woodford S. Van Meter, MD, professor of ophthalmology, Cor- neal and External Disease Service, University of Kentucky, Lexington, has a full-thickness central corneal scar from perforating corneal trauma that involves the stroma and the endothelial layer. Intraoperative risks The two issues Dr. Verdier fears most in PK are elevated posterior pressure and suprachoroidal hemorrhage. "I try to avoid posterior pres- sure problems by placing a Honan balloon at 30 mm Hg for 30 min- utes preop, with additional digital pressure applied for several minutes following peribulbar or retrobulbar and facial nerve blocks," Dr. Verdier said. "Complete lid and extra ocular muscle akinesia is essential. Avoid undue pressure from the lid specu- lum." Ways to avoid suprachoroidal hemorrhage, according to Dr. Verd- ier, include avoiding anticoagulants if feasible and controlling blood pressure, tachycardia, coughing, and anxiety. Also, avoid sudden decom- pression of the anterior chamber upon initial entry. The patient's vision was restored 4 months postop with PK transplant. Dr. Van Meter's pearls for PK—when not performing any lens manipulation—include constricting the pupil preop with pilocarpine and using a 16 blade RK marker to mark the cornea for suturing before the graft is cut. "Pilocarpine not only has the advantage of making the pupil small so that one can center the graft on the optical center of the eye, which is preferable than the center of the cornea, because the two do not always line up, but the small pupil also protects the back of the eye from the procedure," Dr. Van Meter said. The 16 marks around the wound make it easier to place symmetrical sutures. Dr. Van Meter uses a cohesive ophthalmic viscosurgical device in the angle to maintain the angle structures during the case and then irrigates it out midway during the suturing procedure. Phakic vs. pseudophakic Dr. Verdier's phakic eye approach diligently avoids lenticular contact Cornea editor's corner of the world

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