Eyeworld

EW FEATURE 50 All you need to know about cornea transplants • January 2018 ing from right to left detaching the graft, followed by peeling). 10. The DMEK tissue is peeled 80% to 90%, leaving a small hinge. It is not repositioned back on the cornea. 11. A small (2.0 mm) skin biopsy punch is used to trephine the stroma. The peeled DMEK tissue is then repositioned back on the cor- nea by sterile sponges to reverse the flow of liquid and open the DMEK tissue on the cornea. 12. Vacuum is released, and the en- tire corneal tissue is inverted with the epithelial side facing upward. 13. The punched stromal part is removed, exposing the bare DM resting on the stroma. 14. The cleavage hook tip is colored with a skin marker, and a letter "F" is marked on the DM. 15. The punched stromal part is placed back on the cornea. 16. Trypan blue stain is applied on the top of the endothelial cells for 20 seconds and washed briefly with PBS. 17. The corneal tissue is placed in sucrose (hypotonic solution, 1.8%) for evaluation and measurement of ECD, morphology, and trypan blue positive cells. 18. The tissue is fixed using a corne- al claw and stored in the transport medium for shipment. At the Veneto Eye Bank Foun- dation, we have pre-stripped 527 DMEK tissues since May 2014. Fewer than 1% of trypan blue positive cells have been observed; there has been a tissue wastage of less than 6%, including central or peripheral tears, total Descemet's membrane detach- ment, and strong attachment. The low wastage rate and good quality of the grafts have prompted us to use this technique. Complicated tissues like donors with history of severe di- abetes, horseshoe shaped tears, and previous cataract interventions can be managed with this technique. 1 Mauricio Perez, MD, Santiago, Chile I was introduced to DMEK tissue preparation by my former preceptor, David Rootman, MD, and have added some modifications to his original technique. Since I was getting some peripheral tissue tears (both radial and circumferential), we developed a technique of scleral spur disinser- tion prior to endothelium dissec- tion. This scleral spurectomy is performed by doing a manual scleral spur disinsertion 360 degrees using a toothed forceps. Then, I continue the dissection using a Sloane LASEK microhoe, dissecting Schwalbe's line in 360 degrees as described by Dr. Rootman. 2 I continue the dissection of the endothelial layer using a non- toothed forceps. Once I've reached 60% of the dissection, I create a stromal corneal window on the remaining corneal stroma using a 2 mm dermatological punch, which allows me to mark the tissue with the letter "F." This will help me determine tissue orientation during the insertion per the technique described by Mark Terry, MD. Once the tissue has been marked, I complete the dissection with a non-toothed forceps using a rhexis motion. This technique requires a Sloane LASEK microhoe and a standard toothed and non-toothed forceps, a dermatological punch, a marking pen, standard spatula and a stan- dard Barron donor trephine. Since starting the scleral spu- rectomy, this technique has allowed me to save every single tissue for at least 70 DMEK cases. This is espe- cially important in the country I live in where corneal donor tissue is rare, and I cannot allow the loss of any tissue during preparation. If peripheral radial or circum- ferential tears occur, this technique allows for decentration of the final donor during trephination, avoiding the area that might have been dam- aged during tissue preparation. Mark A. Terry, MD, director of corneal services, Devers Eye Institute, and professor of clinical ophthalmology, Oregon Health Sciences University, Portland, Oregon I do not prepare the DMEK tissue myself anymore. I have taught the technicians in our eye bank, Lions VisionGift (LVG), Portland, Oregon, to do this. They prepare dozens of tissues every week so they are better at it than most surgeons, taking the risk of tissue preparation out of the operating suite and into the eye bank. This is for the benefit of the surgeon. They use a technique of Descemet's stripping that leaves a hinge at the edge of the tissue and place an S-stamp on Descemet's membrane to help surgeon orien- tation. They now also offer "pa- tient-ready" preloaded tissue. I recommend that surgeons not strip their own tissue and instead let the eye bank do it for them. If their eye bank does not "pre-strip" DMEK tissue, then their eye bank can send the local tissue to LVG or another processing eye bank to do the preparation for them. Why take the risk when the eye bank can do it all for you? In addition to pre-stripped, pre- marked, pre-stained, and pre-treph- inated tissue, I also use preloaded patient-ready DMEK tissue. We have been using this since March 2017 and now have about 100 cases of DMEK with preloaded tissue. The results are comparable to when we were using pre-stripped tissue but loading it ourselves. However, the advantages of using patient-ready preloaded tissue are enormous. Because the surgery center does not have to buy a trephine, trypan blue, or Straiko injector, there are signifi- cant cost savings. There is increased safety because the surgeon does not have to worry about tissue damage at any of the surgery stages. There are additional savings because with the elimination of tissue preparation and loading of the tissue, there is a much shorter operating room time. The result of using preloaded tissue is a safer, more efficient, and less costly DMEK operation. The clinical results (e.g., graft survival and endothelial cell loss) are no different than when the tissue was prepared by the surgeon. I pre- dict that the use of patient-ready preloaded DMEK tissue will allow more widespread adoption of DMEK surgery in the U.S. and around the world. EW References 1. Parekh M, et al. Standardizing Descemet membrane endothelial keratoplasty graft preparation method in the eye bank experi- ence of 527 Descemet membrane endothelial keratoplasty tissues. Cornea. 2017;36:1458– 1466. 2. Perez M, et al. Fighting tears. The Ophthal- mologist. September 2016. theophthalmolo- gist.com/issues/0816/fighting-tears/ Editors' note: The physicians have no financial interests related to their comments. Contact information Borovik: aborovik@gmail.com Busin: mohit.parekh@fbov.it Parekh: mohit.parekh@fbov.it Perez: mauricioperezvelasquez@gmail.com Tan: reg_tan6@yahoo.com Terry: mterry@deverseye.org Best continued from page 49

• Blank Page
• Blank Page (1)