EyeWorld India June 2015 Issue

Corneal lamellar surgical procedures June 2015 33 EWAP SECONDARY FEATURE rejections, but not as few as with DMEK. Dr. Gorovoy is currently performing and teaching DMEK. The results with DMEK are so far excellent, and both DSAEK and DMEK are superior to penetrating keratoplasty, he said. “Obviously they both replace endothelium, but there’s no stroma carrier involved in DMEK,” Dr. Gorovoy said. The potential for 20/20 vision is well over 50% with DMEK, he said, estimating that this is likely around 20% with DSAEK. DMEK is the next step in the evolution of these procedures, Dr. Gorovoy said. “The problem is if you don’t have a certain volume, you never get past the learning curve,” he said. “I would say if you’re doing DSAEK successfully and you’re a low volume surgeon, just keep doing what you’re doing.” DMEK provides better and faster visual rehabilitation than any of the other endothelial keratoplasty techniques, Dr. Dapena said. “In DMEK no expensive instruments or equipment are needed, so it can be performed in any clinical setting by almost any corneal surgeon with proper training,” she said. “Furthermore, DMEK allows for a more effective use of corneal tissue because out of one cornea, two keratoplasties can be performed.” The anterior part of the cornea can be used for a deep anterior lamellar keratoplasty (DALK) and the posterior layers can be used for DMEK. Dr. Dapena said the main difference between DMEK and DSAEK is graft thickness. In DMEK, an isolated Descemet’s membrane devoid of stroma is transplanted, so the graft is much thinner than in DSAEK, she said. “This means that in DMEK, exactly the same layers that are removed are substituted by donor tissue (Descemet’s membrane and endothelium), whereas in DSAEK a layer of stroma is transplanted also,” Dr. Dapena said. This extra (irregular) layer of stroma presumably decreases the visual quality and/or outcomes of the procedure, she said. Insertion techniques There are a number of techniques for insertion of the tissue in DMEK. Dr. Price is using an IOL injector. Dr. Terry uses an injector that his partner, Michael D. Straiko, MD, designed, based on an already Food and Drug Administration-approved product. “One of the problems in the development of DMEK is that in the U.S., we do not have access to many of the instruments that they are using in Europe,” he said. The injectors specifically are not FDA approved, so surgeons in the U.S. can’t import and use them. This leaves U.S. surgeons using FDA- approved IOL insertion devices on an off-label basis, Dr. Terry said. “There were a lot of problems because they’re designed to push an IOL forward but not designed to push fragile tissue forward.” Dr. Terry has been performing DMEK since 2010 and teaching DMEK since 2012. He said that in 2012, Dr. Straiko began to look at using a glass injector, and instead of developing one from scratch, he took an FDA-approved device, the Jones tube, and used it off-label as an injector. “When we did that, any problems that we had with donor tissue injection went away,” Dr. Terry said. This method makes no-touch loading easy and tissue injection simple. He added that a dry ink “S” stamp on the tissue from the eye bank is making the procedure even easier because the marking allows the surgeon to know the orientation of the tissue at each step of the surgery. This makes it impossible to put a tissue in and have it upside down at the end of surgery, Dr. Terry said, which helps reduce the risk of primary graft failure. Different devices have been designed for the insertion of the DMEK graft inside the eye, Dr. Dapena said. “In our opinion, injectors made of glass rather than plastic are presumably better because they have a smoother surface, probably decreasing endothelial cell damage,” she said. “Furthermore, we would rather not use viscoelastics, which could interfere with graft unfolding or graft adherence to the posterior corneal surface of the patient.” When to use DMEK or DSAEK Dr. Terry is using DMEK for 100% of routine cases of Fuchs’ dystrophy, pseudophakic bullous keratopathy, and failed prior PK. However, there are some cases where he does not use DMEK, including patients with altered anterior segments, anterior chamber IOLs, tubes or trabs, or those who have had a previous extensive vitrectomy. He has previously done DMEK in all of these scenarios (except with anterior chamber lenses), but he said it may not be the best option. The reason for not doing DMEK on these eyes is because the tissue manipulation required and the risk of problems postoperatively do not warrant the improvement of vision that you get going from DSAEK to DMEK, he said. DMEK is for a certain type of eye that needs an endothelial transplant, Dr. Gorovoy said, “and DSAEK is still the required surgery for eyes that aren’t going to be DMEK candidates.” DMEK eyes are those that have almost perfect anterior segments, he said, with normal pupils that can be constricted to 1 to 2 mm, and a well-positioned posterior chamber lens. Dr. Price thinks that if a surgeon is doing a high volume of corneal transplant surgeries, DMEK is the best way to go. It gives better vision with a reduced rejection rate, he said. The problem, however, is that corneal transplants are often done by surgeons who do not do a lot of transplants, so it may be hard to get consistently good results with DMEK. Dr. Price said there were a number of cases he did not do initially with DMEK, including filtering tubes, trabeculectomies, or previous pars plana vitrectomies. Additionally, he said that someone who is aphakic is not recommended for DMEK. “It’s been exciting to see these huge advancements in corneal transplant surgery,” Dr. Price said. Published data that has come out of his site as well as others around the world is starting to show the overwhelming advantages of DMEK compared to DSAEK. As patients are finding out about DMEK, it is increasing the demand for the procedure, Dr. Price said. EWAP Editors’ note: Drs. Dapena, Gorovoy, Price, and Terry have no financial interests related to their comments. Contact information Dapena: Dapena@niios.com Gorovoy: mgorovoy@gorovoyeye.com Price: francisprice@pricevisiongroup.net Terry: MTerry@DeversEye.org