Eyeworld

49 EW FEATURE January 2018 • All you need to know about cornea transplants tissue is tightly attached, it can be peeled using a quadrant method or oscillating fashion (gently mov- mm Barron trephine. The newly cut edges are again stained with trypan blue, and the peeling is completed. It is recommended to start prac- ticing DMEK graft preparation in the wet lab. Ask for practice corneas that are from donors 55 years or older with no history of diabetes. Also, feel how Descemet's mem- brane behaves, and note the amount of tension it can withstand before tearing. This is what makes DMEK preparation appealing. No special instruments are required other than a few trephine punches and the microfinger instrument. With our technique, we are able to prepare DMEK tissue safely and successfully most of the time. Mohit Parekh, PhD, research scientist, Veneto Eye Bank Foundation, Venice, Italy, and Massimo Busin, MD, Department of Ophthalmology, Villa Igea Hospital, Forli, Italy 1. The endothelial cell density (ECD) and mortality is checked before is- suing the human donor cornea for transplantation. An ECD of >2,200 cells/mm 2 with <2% mortality is considered suitable in our eye bank for DMEK. 2. We use a SCUBA technique with minor modifications as described below. 3. The tissue is fixed on a suction block by creating vacuum with endothelial side facing upward. 4. A donor trephine (9.5 mm) is gently tapped on the endothelial surface to obtain a superficial cut. 5. The cut margins are made visible after staining it with trypan blue (0.25%). The stain is washed off with phosphate buffered saline (PBS). 6. The peripheral endothelium is re- moved, and the tissue is restained to differentiate between the remaining central endothelium and the bare stroma left after the excision of the peripheral endo- thelium. 7. A small drop of tissue culture medium is added topically on the endothelium to keep the cells moist while stripping. 8. A cleavage hook is used to iden- tify the plane of cleavage (moved radially along 360-degree circum- ference), slightly detaching the DMEK graft at the periphery. 9. An anatomic forceps with 1.2 mm pointed tips is used to peel the tissue from the superior side to- ward the inferior. This step can be performed as a single peel method or a quadrant method depending on the attachment of the Descem- et's membrane to stroma. If the ® 973-989-1600 • 800-225-1195 • www.katena.com Barron Vacuum Trephines Trusted. Proven. "Seamlessly" perfect. Barron Blade Want a perfect cut? Want a perfect cut? BEWARE OF THE SEAM Not all trephines are the same Not all trephines are the same THE PERFECT BLADE The blades used in many vacuum trephines are produced from inexpensive flat razor stock that is cut, rolled and glued into place. While this saves the manufacturer expense, it produces a blade with a problem — a seam. During use, the edges of this seam drag in the tissue producing a less than perfect cut. Only the blade in a Barron Radial Vacuum Trephine is produced from a solid rod of stainless steel. That's right, a solid rod. It is precisely drilled, honed and sharpened through four proprietary grinding processes to produce a perfectly round, dimensionally accurate blade. continued on page 50

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