EyeWorld India March 2018 Issue

March 2018 14 EWAP FEATURE Best practices for DMEK tissue preparation by Vanessa Caceres EyeWorld Contributing Writer AT A GLANCE • DMEK can be a challenging procedure. However, nding a way to conquer tissue preparation can make this approach easier. • Surgeons have different techniques they use for DMEK tissue preparation. These are especially important internationally, where there may not be access to pre-stripped DMEK tissue. • The use of pre-stripped and preloaded DMEK tissue makes DMEK easier and less costly for some corneal specialists. Overcoming the challenges of tissue preparation can facilitate better use of DMEK I t can take some finesse to prepare tissue for Descemet’s membrane endothelial kera- toplasty (DMEK). However, DMEK can require fewer resources to perform in the OR, so it has its advantages. Here’s how some surgeons from across the globe approach DMEK tissue preparation and how the use of pre-stripped DMEK tissue can make a difference. Armand Borovik, MD, Southern Ophthalmology, Sydney, Australia I use a technique where instead of scoring the tissue with a sharp instrument or trephining with a blade, I use a blunt instrument (a Rootman-Goldich modified Sloane's LASEK microhoe devel- oped by David Rootman, MD) to find an anatomical plane of dissection beginning within the trabecular meshwork. I first stain the tissue with trypan blue to help identify the meshwork better. After scraping free 1 to 2 mm of the peripheral tissue for 360 degrees, I use a for- ceps to peel the membrane into a “taco formation” (i.e., folded over 50%). I then make a 3-mm stromal punch through which I can mark the stromal side of Descemet’s membrane with an “F.” This is done using gentian violet from a marking pen on the tip of the microhoe that was used for the initial peel for the “F” and the tip of a forceps for the “.”. I then do a partial thickness trephination of the tissue to the desired graft size and complete the peel. After staining the tis- sue with 100% trypan blue for 2 minutes, I aspirate the tissue into a glass injector, and it is ready for insertion. Before injecting the graft, I always check to see where the scrolled tissue makes a “V” and ensure this is facing up while the graft is injected. It is critical to practice the technique in the wet lab prior to preparing the tissue for surgery as it is important to learn how the tissue behaves. I always work under balanced salt solution as this decreases tissue tension and de- creases the chance of a tear. Also, make sure that you tilt the surgical microscope 30 degrees to decrease reflections. Never force the tissue; be patient and make small, slow, fine movements. If you do have a tear, it is useful to mark the scleral rim with a marking pen at that point so you are conscious of where it is and start again from a point away from that tear. Watching videos or attending a course with experts in DMEK tissue preparation, particularly if there is a wet lab component, are very useful when first learning this technique. Reginald Robert Tan, MD, clinical fellow, cornea, external disease and refractive surgery, University of Ottawa Eye Institute, Ottawa, Canada At our center, under the direc- tion of Kashif Baig, MD, we perform a modified submerged cornea using backgrounds away (SCUBA) tech- nique to prepare DMEK tissue. The first step with SCUBA involves placing the corneoscleral donor tissue endothelial side up on an 8-mm Barron trephine punch block (the size will depend on the patient’s white-to-white distance). After centering the cornea, we do a partial thickness punch using a 10-mm corneal trephine. This limits our initial flap edge dissec- tion within this diameter. Other techniques usually start the De- scemet’s separation by dissecting the trabecular meshwork from its attachment with the scleral spur down to Schwalbe’s line. However, we noticed that starting dissection from the 10-mm diameter edge decreased the occurrence of tears. After staining the 10-mm borders with a few drops of trypan blue, the endothelium is com- pletely submerged in balanced salt solution. A microfinger dis- sector instrument (Moria Surgical, Antony, France) is used to delineate at least 180 degrees of peripheral Descemet’s membrane from the stroma. Using a curved microty- ing forceps, half of the Descemet’s membrane is then carefully peeled off and left in a taco configuration. We then create a 2-mm full thickness window on the exposed stroma using a dermatologic punch. After placing the Descem- et’s membrane back into position, we flip the whole corneal button and place an “F” mark on the Descemet’s membrane side of the graft through the stromal window. The cornea is flipped again en- dothelial side up, followed by a partial thickness punch with the 8-mm Barron trephine. The newly