Eyeworld

59 EW FEATURE January 2018 • All you need to know about cornea transplants DMEK tissue trephined at 8 mm so I have a 0.5 mm difference between donor and recipient," he said. Pre-marked DMEK tissue Dr. Veldman said he is a big propo- nent of pre-marked DMEK tissue, having been involved in the devel- opment of the S-stamp. "It has im- proved the safety margin in DMEK through a reduction in the rate of upside down graft implantations and importantly, in our studies, did not significantly impact clinical out- come parameters, including rebub- ble rate and 6-month endothelial cell loss." 1,2 He has been heartened by the number of physicians who have told him that the S-stamp enabled their successful and safe adoption of DMEK. "That said, there is some limited regional endothelial trauma induced secondary to the applica- tion of the S-stamp, so I will typical- ly position the graft so that the S is superior, allowing more prolonged gas bubble coverage postoperative- ly," he said. Dr. Lee uses pre-marked tissue in all DMEK cases. The eye bank pre- strips the tissue, leaving one marked edge attached, and places an "S" mark on the Descemet's membrane side. "I think it is a godsend," Dr. Suh said of pre-marked tissue. "It facili- tates the surgery. For the beginning surgeons where the trypan blue can start to fade with longer unfolding times, the S-stamp will help with orientation." She only uses S-stamp tissue at this point in her practice. Cases to watch for early in the learning curve Dr. Lee suggested avoiding young donor tissue, as it is hard to unscroll in the eye. "Start out with pseu- dophakic patients rather than com- bined cataract patients," he said. Additionally, he suggested avoiding highly myopic eyes with high axial lengths, as well as patients with prior glaucoma surgery. Dr. Suh said she would avoid any eyes that have very deep ante- rior chambers, as the tissue is more difficult to unfold. "Also, any eyes that have had glaucoma surgery and vitrectomized eyes are better DSAEK candidates," she said. "I stress to surgeons adopting DMEK to avoid eyes that have had prior vitrectomy," Dr. Veldman said. "Vitrectomized eyes simply do not allow adequate anterior chamber shallowing for those of us who use external tapping techniques." He added that if you ask experienced DMEK surgeons, they will tell you that some of their most stressful and extended DMEK experiences were on vitrectomized patients. "I am hopeful that this may change in the future with the emergence and ongoing validation of pull-through DMEK techniques that allow direct control of the graft," he said. "Until then, DSAEK is a great procedure in these eyes in my opinion." How to manage the bubble Dr. Lee makes an inferior iridecto- my prior to tissue insertion. "I use 100% air fill once the DMEK tissue is centered and keep the patient flat for an hour in the recovery room, then check in the YAG laser room at the slit lamp and make sure the air clears the iridectomy," he said. If it does, the patient is discharged. If it does not, he will release a small amount of air at the lamp and let the patient sit flat for 30 more min- utes and recheck prior to discharge. Dr. Veldman typically creates an iridectomy using a scratch down technique, which he subsequently enlarges with intraocular micro-scis- sors, including removal of a small piece of peripheral iris tissue. "A good peripheral inferior iridectomy allows me to place a large, approx- imately 90% fill of 20% concen- tration SF6 gas," he said. "With an adequate bubble in place, I use my finger to apply pressure to the sclera, with resultant elevation of the intraocular pressure for a few 20–30 second cycles. I will typically have patients position for about 45 minutes, after which they sit up until I can check the adequacy and aqueous clearance of the iridecto- my." If there is not an inferior fluid meniscus that is contiguous with the iridectomy, Dr. Veldman will burp the smallest possible amount of gas from the inferior paracentesis and recheck the patient in 5 min- utes, at which point there is typical- ly a visible meniscus. Dr. Suh uses 20% SF6 and fills up to a large bubble size. She uses the anterior vitrectomy unit to make the inferior iridectomy. "But make sure that when the patient is sitting up and facing forward, there is clearance of the inferior iridecto- my," she said. EW References 1. Veldman PB, et al. Stamping an S on DMEK donor tissue to prevent upside-down grafts: laboratory validation and detailed preparation technique description. Cornea. 2015;34:1175–8. 2. Veldman PB, et al. The S-stamp in Descem- et membrane endothelial keratoplasty safely eliminates upside-down graft implantation. Ophthalmology. 2016;123:161–4. Editors' note: The physicians have no financial interests related to their comments. Contact information Lee: wblee@mac.com Suh: lhs2118@cumc.columbia.edu Veldman: peterbveldman@gmail.com Poll size: 88 Which of the following statements about DMEK surgery applies to you? I refer my patients to a cornea specialist I perform DMEK surgery now I plan to begin performing DMEK surgery in the next 6 months I plan to continue per- forming DSAEK surgery for now until DMEK surgery becomes easier What I find most challenging about DMEK surgery is: Preparing the donor tissue Injecting the donor tissue Unfolding the donor tissue Air bubble management Postoperative man- agement (i.e., DMEK detachment rebubbling)

• Blank Page
• Blank Page (1)