EyeWorld India March 2018 Issue

EWAP FEATURE 19 Alternative procedures seek to reduce stress on limited supply of donor corneas by Liz Hillman EyeWorld Staff Writer AT A GLANCE • With a shortage of donor corneas for patients who need endothelial keratoplasty, newer techniques are being developed to more ef ciently use available donor tissue or eliminate the need for it altogether. • Pre-Descemet’s endothelial keratoplasty 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 cultivation 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. PDEK, primary Descemetorhexis without a graft, and cultivated endothelial cells seek to serve more patients with corneal disease S ince Gerrit Melles, MD, PhD , first described posterior lamellar kerato- plasty in 1998, there has been a revolution in techniques to avoid a penetrating keratoplasty (PK) in cases where a full-thickness trans- plant might not be needed, such as deep lamellar endothelial kerato- plasty (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 ef- ficiently utilizing or reducing dependence on donor tissue, result- ing 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. Agarwal’s Eye Hospitals, Chennai, India, Kathryn Colby, MD, PhD , chair, Department of Ophthalmol- ogy and Visual Science, Univer- sity of Chicago Pritzker School of Medicine, Chicago, and Jodhbir Mehta, MD , associate professor, Singapore National Eye Centre, discuss pre-Descemet’s endothe- lial keratoplasty (PDEK), primary Descemetorhexis without a graft, and cultivated corneal endothelial cells, respectively, sharing surgical basics, patient selection, and cur- rent findings/status of the tech- nique. Pre-Descemet’s endothelial keratoplasty According to Dr. Agarwal, PDEK is “a variant of endothelial kerato- plasty,” combining the advantages of DSEK and DMEK. The advantage of DSEK is a thicker graft from the donor, making it easier for the sur- geon to prepare, insert, and manip- ulate in the recipient’s eye. But this graft, which ranges from 100–150 µm thick, adds to the overall cor- neal thickness after transplant and, as Dr. Agarwal put it, this means the endothelium 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 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 lay- ers from the residual stromal bed. Trypan blue is injected into the big PDEK pre- and postop with a young donor shows clearance of the severe corneal haze. Source: Amar Agarwal, MD continued on page 20 March 2018