CORNEA EWAP SEPTEMBER 2023 33 Marcus Ang, MD Head, Senior Consultant, Associate Professor Cornea Service, Singapore National Eye Center 11 Third Hospital Avenue, Singapore 168751 marcus.ang@snec.com.sg ASIA-PACIFIC PERSPECTIVES Performing DMEK in Asian eyes with preexisting glaucoma can be challenging. These eyes often have shallow anterior chambers, floppy iris and peripheral anterior synechiae that can make donor insertion and graft manipulation challenging. In many Asian eyes with shorter axial lengths and higher vitreous pressure, intraoperative graft extrusion of the DMEK donor can occur if injected into the eye. We usually perform pull-through, endothelium-in techniques in eyes with previous angle closure as this allows for a stable anterior chamber during donor insertion. Immediate postoperative optimization of intraocular pressure (IOP) with close monitoring is important. We recommend a prophylactic peripheral iridectomy to prevent reverse pupillary block, and patients should posture face-up and be evaluated regularly, as patients may be asymptomatic despite raised IOP. Glaucoma was also reported to be associated with iris damage and, subsequently, postoperative chronic inflammation and endothelial cell loss in DMEK. Thus, postoperative management of intraocular pressure and prevention of steroid response with an optimal taper of topical steroids are key to preventing exacerbation of glaucomatous optic neuropathy, while preventing endothelial cell attrition. References 1. Ang M, Sng CCA. Descemet membrane endothelial keratoplasty and glaucoma. Curr Opin Ophthalmol. 2018 Mar;29(2):178-184. 2. Ang M, Ting DSJ, Kumar A, May KO, Htoon HM, Mehta JS. Descemet Membrane Endothelial Keratoplasty in Asian Eyes: Intraoperative and Postoperative Complications. Cornea. 2020 Aug;39(8):940-945. Editors’ note: Dr. Ang disclosed no relevant financial interests. “After [DMEK] surgery, we put them in a state where their glaucoma control may be jeopardized because we’re giving them long-term steroid therapy that can affect the pressure. You have to have them well controlled. … We don’t want to put another factor into the equation if they’re not stable,” Dr. Sorkin said. Dr. Deng said that the patient should be able to add at least two IOP-lowering medications to their regimen prior to DMEK surgery because they might need them to manage an increased IOP postop due to corticosteroid use. In addition to medication considerations, Dr. Sorkin said that if the glaucoma patient has a tube, the position of that tube in the anterior chamber should be considered because it could interfere with the graft. If it’s too long, it should be trimmed prior to or in combination with DMEK surgery. The tube could also be repositioned to put it posteriorly, Dr. Sorkin said. He said there is speculation that when the tube is too close to the graft, aqueous flow could damage the endothelium, reducing the length of graft survival. Other factors also negatively affect the long-term survival of corneal transplants in eyes with prior trabeculectomy and shunt, Dr. Deng said. Surgical considerations When it comes to DMEK surgery in patients with glaucoma, Dr. Deng said that eyes with prior tube shunts or trabeculectomy might have anterior or posterior synechiae that needs to be lysed during the DMEK procedure. Dr. Sorkin said both of these filtration procedures could also filter out the air that is needed for the graft attachment more quickly. He said a bigger air fill might be needed or the patient can be positioned afterward in such a way to reduce this chance. Dr. Deng said that she doesn’t change much of what she does preop, intraop, or postop for patients who have had prior MIGS vs. trab/tube. Postop considerations Both Dr. Deng and Dr. Sorkin emphasized the importance of regular IOP monitoring in the postop period for DMEK patients who have glaucoma. Dr. Deng said she will check IOP 1–2 hours after DMEK surgery in the postop area, and she has a low threshold to burp the paracentesis to lower the IOP if it is over the mid-20s at the bedside using a portable slit lamp. Dr. Sorkin also cautioned against a high IOP in the early postop period, due to the air bubble potentially blocking the trab and/or causing pupillary block. “If I see a big air fill, especially a couple of hours after surgery when I check these patients, I will have a lower threshold for removing some of the air at the slit lamp to avoid reaching the status of pupillary block because I don’t want them to have an IOP spike,” he said. He also said that when measuring IOP in the early postop period, try to use a low to no-contact tonometer to avoid potentially dislocating the graft. Later in the postop period, IOP needs continued monitoring due to the prolonged steroid use. Dr. Deng and Dr. Sorkin said that the cornea specialist and glaucoma specialist, which in some cases might be the same surgeon, should
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