EyeWorld Asia-Pacific March 2014 Issue

42 EWAP CORNEA March 2014 Pre Descemet’s endothelial keratoplasty (PDEK): A novel method of endothelial transplantation by Amar Agarwal, MS, FRCS, FRCOpth A new method incorporates the recently discovered pre Descemet’s collagen layer dubbed Dua’s layer into the procedure T he problems with the existing procedure of endothelial transplantation are difficult graft handling, intraoperative unrolling of the graft roll, and tissue loss during surgical manipulation. This has been overcome by our recent innovative technique in which a thicker graft than the conventional Descemet’s membrane endothelial keratoplasty (DMEK) is used. We call it pre Descemet’s endothelial keratoplasty (PDEK). Recently, Harmindar Dua, MD , University of Nottingham, UK, identified the presence of the pre Descemet’s collagen layer, which differed in several properties from the overlying posterior stroma. After learning the nature of the pre Descemet’s layer (Dua’s layer), this concept of transplanting the pre Descemet’s layer along with Descemet’s membrane (DM) has begun in collaboration with Dr. Dua. Pre Descemet’s endothelial keratoplasty (PDEK) involves the transplantation of the DM with endothelium along with the pre Descemet’s (Dua’s) layer. Donor graft preparation A corneoscleral disc with an approximately 2-mm scleral rim is dissected from the whole globe or obtained from an eye Recipient bed preparation and graft insertion. 1. Preop image of the eye with endothelial decompensation. Epithelial debridement being done. 2. Trephine marking done on the cornea. 3. Descemet’s membrane scored and stripped with reverse Sinskey hook. 4. Graft lenticule is loaded into an injector. 5. Intraoperative manipulation of the graft for proper positioning. 6. Air injected underneath the donor graft lenticule to lift it toward the recipient posterior stroma. Anterior chamber filled with air. Source: Amar Agarwal, FRCOphth bank. A 30-gauge needle attached to a syringe is inserted from the limbus into the mid-peripheral stroma Air is slowly injected into the donor stroma until a type 1 big bubble is formed; this is a well-circumscribed, central dome- shaped elevation measuring 7.5 mm to 8.5 mm in diameter It always starts in the center and enlarges centrifugally, retaining a circular configuration. Trephination of the donor graft is done along the margin of the big bubble The bubble wall is penetrated at the extreme periphery, and trypan blue is injected into the bubble to stain the graft, which is then cut all around the trephine mark with a pair of corneoscleral scissors and covered with the tissue culture medium. The graft is loaded into an injector when ready for insertion. Recipient bed preparation After administering peribulbar anesthesia, the recipient corneal epithelium is debrided, if grossly edematous, for better visualization A trephine mark is made on the recipient cornea respective to the diameter of the Descemet’s membrane to be scored on the endothelial side A 2.8-mm tunnel incision is made at 10 o’clock near the limbus. The anterior chamber is formed and maintained with saline injection or infusion. The margin of the Descemet’s membrane to be removed is scored initially from the endothelial side with a reverse Sinskey hook Once an adequate edge is lifted, non- toothed forceps are used to gently grab the Descemet’s membrane at its edge, and the graft is separated from the underlying stroma in a capsulorhexis-like circumferential manner. The peeled Descemet’s membrane is then removed from the eye. Donor lenticule implantation The donor lenticule roll (endothelium-Descemet’s membrane-PDL) is inserted in the custom-made injector and slowly pushed up the lumen of the nozzle. The injector is improvised from an IOL implant injector by removing the sponge tire and spring and reattaching the sponge tire, to prevent any back suction and inadvertent damage to the donor graft. Using the injector, the graft roll is injected in a controlled fashion into the anterior chamber. The donor graft is oriented endothelial side down and positioned on to the recipient posterior stroma by careful, indirect manipulation of 1 4 2 5 3 6