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EW CORNEA 34 August 2015 Berdahl said the use of gas increases the likelihood of graft attachment. He places sutures that are absorbable that do not have to be removed postoperatively. "I think DMEK gives better visu- al outcomes, faster visual recovery, and there is a lower rejection rate with DMEK," he said. Another bene- fit is that preparation of isolated Descemet's grafts is not as resource- intense, which can increase the overall availability of donor tissue. Despite these advantages, DSEK continues to be performed in much greater numbers than DMEK, Dr. Berdahl said. EW Editors' note: Dr. Berdahl has no finan- cial interests related to this article. Contact information Berdahl: john.berdahl@vancethompsonvision.com by Louise Gagnon EyeWorld Contributing Writer are not very dependable for inform- ing a clinician's decision of whether to perform either type of endothelial keratoplasty, he said. "There can be enormous vari- ability [in terms of what qualifies as a normal cornea]," Dr. Berdahl said. "We have seen corneas that have thicknesses of 490 microns or 620 microns and are normal." Removing the dysfunctional en- dothelium is more easily done when the patient with Fuchs' dystrophy presents with a more advanced con- dition, Dr. Berdahl said. Placing the donor tissue and getting the graft to unfold in the eye is a technical chal- lenge for the surgeon, he stressed. When placing the endothelial graft, Dr. Berdahl injects fluid into the eye with a goal to have the graft unfold. Once the graft is centered, Dr. Berdahl uses gas to create a bubble underneath the donor tis- sue. While air is typically injected underneath the donor tissue, Dr. reinject air, leading to postoperative bubble. Fear of postoperative bubble as well as the perceived complexity of DMEK is likely preventing more surgeons from performing DMEK, Dr. Berdahl said. When a co-pathol- ogy like glaucoma is present, it is preferable to perform a DSEK instead of a DMEK, he added. "DMEK is a very different and very delicate surgery. You are relying on fluid currents to get the result that you want. You are manipulat- ing fluids rather than tissues," Dr. Berdahl said. "Once you get through the learning curve, it's well within the skill set of corneal surgeons who are already doing DSEKs." Various measures can be used to determine if a DMEK or DSEK should be performed, Dr. Berdahl said. Some of those measures in- clude pachymetry, endothelial cell counts, a guttata assessment, and the presence of intrastromal corneal edema. These measures, however, The procedure may be difficult, but it offers advantages like better vision and faster rehabilitation D escemet's membrane endothelial keratoplasty (DMEK) is a more difficult operation than Descemet's stripping endothelial kera- toplasty (DSEK), but the former type of endothelial keratoplasty produces better visual acuity, less rejection of donor tissue, and more rapid visual rehabilitation, said John Berdahl, MD, in practice at Vance Thompson Vision, Sioux Falls, S.D., and medical director of the South Dakota Lions Eye Bank. "The difference is that when you do a DSEK, you include the stroma, while the DMEK only replaces the endothelium and Descemet's membrane," Dr. Berdahl told attendees of the annual Toronto Cataract Course, organized by the University of Toronto's Department of Ophthalmology & Vision Scienc- es. "There is no stroma whatsoever [that is transplanted] with DMEK." Dr. Berdahl was asked to per- form a DMEK on his father, a patient who had Fuchs' dystrophy and who worked for the South Dakota Lions Eye Bank. Dr. Berdahl's father's vi- sion complaint was glare that made him unable to perform activities like driving at night. "My goal in 2014 was to become facile at performing DMEK," Dr. Berdahl said in an interview. "My fa- ther requested that I do the [partial corneal] transplant [procedure]." After undergoing DMEK, Dr. Berdahl's father no longer com- plained of glare, had 20/20 vision but required glasses for close read- ing, and was able to perform daily activities, including driving at night. Dr. Berdahl measured his father's en- dothelial cell counts postoperatively, and they rose significantly. "I think the visual acuity with DMEK is better, but it is more tech- nically challenging," Dr. Berdahl said. "It's more common to have postoperative bubble [with DMEK than with DSEK]." With concerns about graft detachment because of the fragility of the donor tissue, surgeons may DMEK advantages Trypan staining of prepared DMEK tissue Partially detached DMEK Source: John Berdahl, MD

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