Eyeworld

EW FEATURE 52 All you need to know about cornea transplants • January 2018 AT A GLANCE • With a shortage of donor corneas for patients who need endothelial kera- toplasty, newer techniques are being developed to more efficiently use available donor tissue or eliminate the need for it altogether. • Pre-Descemet's endothelial kera- toplasty pulls the pros from both DMEK and DSEK into one procedure and allows for younger donor tissue to be used. • Donor corneas can be used to treat dozens of patients with a cell culti- vation technique, transplanted via a carrier or direct injection. • In some cases, a patient's own intact peripheral endothelial cells can repopulate an area of Descemet's stripping (descemetorhexis) without the need for a graft. by Liz Hillman EyeWorld Staff Writer touch it, and it tears," Dr. Agarwal said. In PDEK, the graft is not only thinner than a DSEK graft (25 µm), but physicians use younger donors. In fact, Agarwal et al. showed how it was possible to use infant corneas for this purpose. 3 The PDEK graft, which includes the pre-Descemet's layer (Dua's layer), Descemet's membrane, and endothelium, is created using a 30-gauge needle connected to a syringe bevel up to enter the stroma and inject air to form a type 1 big bubble. The air separates these layers from the residual stromal bed. Trypan blue is injected into the big bubble to stain the graft and scissors finish the dissection. The graft is then loaded into an injector. Various eye banks are already producing PDEK grafts, making it possible for the surgeon to only have to stain the graft with trypan blue and load it into the injector, Dr. Agarwal said. For transplant, Dr. Agarwal stressed the importance of using a trocar anterior chamber maintainer. With air on via the AC maintain- er, perform the descemetorhexis, scoring, and stripping with a reverse Sinskey hook. Once the patient's Descemet's is removed, turn the air off for insertion of the graft. Once it begins to unroll, inject air so the graft sticks against the overlying stroma, restarting air infusion after- ward, Dr. Agarwal explained. Use a reverse Sinskey hook to spread out the graft, smoothing wrinkles. Primary Descemetorhexis without a graft, PDEK, and cultivated endothelial cells seek to serve more patients with corneal disease S ince Gerrit Melles, MD, PhD, first described poste- rior lamellar keratoplasty in 1998, there has been a revolution in techniques to avoid a penetrating keratoplasty (PK) in cases where a full-thickness transplant might not be needed, such as deep lamellar endothelial keratoplasty (DLEK), Descemet's stripping endothelial keratoplasty (DSEK), and Descemet's membrane endothelial keratoplasty (DMEK). 1 Newer procedures are in the works with the goal of more effi- ciently utilizing or reducing depen- dence on donor tissue, resulting in positive patient outcomes. One global survey found that there is only one donor cornea available per 70 patients who might need it. 2 The authors of this survey wrote that "it is also essential to develop alternative and/or complementary solutions, such as corneal bioengi- neering." Amar Agarwal, MD, Dr. Agar- wal's Eye Hospitals, Chennai, India, Kathryn Colby, MD, PhD, chair, Department of Ophthalmology and Visual Science, University of Chicago Pritzker School of Medi- cine, Chicago, and Jodhbir Mehta, MD, associate professor, Singapore National Eye Centre, discuss pre-De- scemet's endothelial keratoplasty (PDEK), primary Descemetorhexis without a graft, and cultivated cor- neal endothelial cells, respectively, sharing surgical basics, patient selec- tion, and current findings/status of the technique. Pre-Descemet's endothelial keratoplasty According to Dr. Agarwal, PDEK is "a variant of endothelial keratoplas- ty," combining the advantages of DSEK and DMEK. The advantage of DSEK is a thicker graft from the do- nor, making it easier for the surgeon to prepare, insert, and manipulate in the recipient's eye. But this graft, which ranges from 100–150 µm thick, adds to the overall corneal thickness after transplant and, as Dr. Agarwal put it, this means the en- dothelium has to "pump out more fluid. That is the problem in DSEK," he said. Conversely, in DMEK, the graft is only 15 µm, but Descemet's is stuck to the stroma until an older age, necessitating the use of older donors. The thinness of the graft also makes it very fragile. "We just Alternative procedures seek to reduce stress on limited supply of donor corneas PDEK pre- and postop with a young donor shows clearance of the severe corneal haze. Source: Amar Agarwal, MD continued on page 54 "If you are an endothelial kera- toplasty surgeon—or even if you are not—you can certainly learn PDEK," Dr. Agarwal said, adding that there are some minor surgical differences when compared to DSEK and DMEK and reiterating the importance of a trocar AC maintainer in PDEK cases. Dr. Agarwal said PDEK can be performed in all cases requiring some form of EK, including pre- viously failed grafts. In November 2017, Dr. Agarwal published the first book on PDEK, which includes the various ways of how to surgically perform the procedure and the sur- gical techniques, such as a glued IOL or iris repair with his relatively new four-throw pupilloplasty technique. 4 Primary descemetorhexis As in PDEK, DMEK, and DSEK, be- fore a graft can be inserted into the recipient eye, the patient's Descem- et's membrane must be stripped off. But what if it were left that way, stripped and with no graft? About 5 years ago, small case reports started to be published about failed DMEK grafts that sponta- neously cleared in Fuchs' patients, use of a rho kinase inhibitor to clear the cornea without a graft, and deliberate descemetorhexis without a graft with mixed results. 5–8 This research had Dr. Colby testing the technique of a primary descemetorhexis in 2014 on one of her long-term Fuchs' patients who was scheduled for cataract surgery. At 1 month, this patient's cornea had cleared and his vision was Amar Agarwal, MD, presents 15 steps to PDEK

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