EyeWorld Asia Pacific is the news and feature magazine of APACRS, KSCRS, and COS. EyeWorld Asia-Pacific serves as the premier publication for anterior segment surgeons in the Asia-Pacific region.
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50 EWAP cornEA December 2016 Practice makes perfect Going lamellar means overcoming a steep learning curve M astering new and challenging surgical techniques can take practice—sometimes a lot of it. Corneal lamellar transplant procedures have evolved into highly sophisticated surgical techniques that spot treat diseased corneal layers and spare healthy tissue, while offering patients better visual outcomes, quicker healing, and reduced graft rejection, compared to penetrating keratoplasty. However, acquiring the right skills takes patience and dedication. The evolution of DMEK can be chalked up to due diligence and a good dose of lateral thinking, according to corneal transplant surgeon Walter Sekundo, MD, head, Department of Ophthalmology, Philipps University, Marburg, Germany, who thinks that the road to skilled keratoplasty can be a long one. "Lamellar keratoplasty takes time to learn. We all have a learning curve when we start something new. You might realistically have to perform close to 100 grafts before you beat the learning curve and your results become consistently good," he said in an interview with EyeWorld, speaking about a presentation he gave on the subject at the Ophthalmologicum Balticum Congress in Riga, Latvia. He said that the importance of surgical experience in graft surgery is not only for the success of surgery, but also for graft survival. 1 The graft DMEK is a partial-thickness cornea transplant procedure that involves the selective removal of diseased portions of the Descemet's membrane and endothelium and the subsequent transplantation of a fitted donor graft. Based on his experience from more than 800 DMEK surgeries performed at his institute in Marburg, Dr. Sekundo considers DMEK graft preparation an important part of the surgery itself. "Preparing the graft is the first step of surgery and it is, in my opinion, more difficult than the surgery itself. It is advantageous to harvest the DMEK graft immediately prior to surgery," he noted. "In our institute, the surgeon that performs the surgery also creates the graft, which may take 15 to 20 minutes. We always take the white-to-white measurement of the recipient to adjust the graft size. Generally, we cut the graft 3 millimeters smaller than the white-to-white measurement to allow enough room for the graft within the cornea. We worked out some tricks over time to get the measurement right. We also make sure that the descemetorhexis is larger than the graft diameter," Dr. Sekundo said. "Some surgeons, particularly those who do not operate in large numbers, buy corneal bank- prepared DMEK grafts. These are more expensive, however, if you only do three or four a month, you may not have enough experience to prepare the Descemet's membrane and endothelium safely and you run the risk of wasting the cornea. We are a fairly high volume institution and have become skilled in graft preparation. We've prepared more than 800 grafts, with only one case where we had to abandon a cornea, in which it was absolutely impossible to prepare the DMEK roll. We prepare corneal grafts under fully sterile conditions in the operating theater while the patient is getting prepped for surgery in the neighboring theater. Both theaters have an internal connecting door," he explained. He elucidated that the donor corneal age should not be below 45 years. Descemet's rolls harvested from younger eyes can be tight and therefore difficult to unroll completely without coming into contact with the cornea, which can damage the to-be-grafted endothelial cells and lead to graft failure. 2 The older the graft, the thicker Descemet's membrane is likely to be. "Descemet's membrane has two distinct layers, the anterior layer made of collagen lamellae and proteoglycans and the posterior layer produced by the endothelial cells. This posterior layer is the part that is laid down, and it is thicker with age. Other surgeons prefer to take grafts from donors that are more than 60 years. However, older corneas may make poorer grafts in terms of vitality of endothelial cells. We are quite satisfied with the 45-year cut-off." Endotamponade In the classic Melles' technique after injecting the graft, the surgeon unrolls and positions it in the anterior chamber by pushing the graft against the iris by an air bubble. Thereafter, this bubble is aspirated and replaced by another bubble under the graft supporting by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer At the conclusion of the DMEK surgery, the blue stained graft is unfolded and pushed against the host cornea by a 5% SF6 gas bubble. Source: Walter Sekundo, MD