GLAUCOMA EWAP MARCH 2022 57 reclose the conjunctiva and not have another erosion in the vast majority of cases. “If we see something that predisposes to erosions, like the tube shunt is a little too anterior in insertion or if it has a laxity to it so the tube bows up, most of us would reposition,” Dr. Myers said. “But for most of the patients, another patch graft on top, deepithelialize the area with cautery, and make sure that fresh conjunctiva is brought down that’s not under tension.” Even with long-term follow up, it’s rare the patient gets a second erosion, he said, though he noted it can happen. “I think in any patient who has an infection and erosion, you have to assume it’s from the erosion,” Dr. Myers said. The erosion is usually easy to identify, but he added that nonglaucoma specialists may not be specifically looking for this. Dr. Myers added that the further back from the limbus that the tube is inserted, the less likely it is to have erosion. A tube that’s placed in the sulcus, in general, tends to enter the eye more posterior. A tube in the pars plana is even more posterior. “When it doesn’t extend as far anterior to the limbus, I think the risk of erosion is much smaller,” he added. Dr. Myers said it’s always a balance of pros and cons. People with good tissue do better, and the better the placement, the better they tend to do, but there are some patients who still run into problems. Eyes that had prior surgery and those with tissue and surface issues are more at risk as well, he said. Careful vigilance in eyes with prior tube shunt surgery will identify erosions early before serious problems arise in most cases. EWAP References 1. Trubnik V, et al. Evaluation of risk factors for glaucoma drainage devicerelated erosions: A retrospective case-control study. J Glaucoma. 2015;24:498–502. 2. Liu KC, et al. Recurrent tube erosions with anti-vascular endothelial growth factor therapy in patients with age-related macular degeneration. Ophthalmol Glaucoma. 2020;3:295–300. 3. Gedde SJ, et al. Postoperative complications in the Tube Versus Trabeculectomy (T6T) study during five years of follow-up. Am J Ophthalmol. 2012;153:804–814. 4. Oana S, Vila J. Tube exposure repair. J Curr Glaucoma Pract. 2012;6:139–142. 5. Chaku M, et al. Risk factors for tube exposure as a late complication of glaucoma drainage implant surgery. Clin Ophthalmol. 2016;10:547–553. 6. Muir KW, et al. Risk factors for exposure of glaucoma drainage devices: a retrospective observational study. BMJ Open. 2014;4:e004560. 7. Levinson JD, et al. Glaucoma drainage devices: risk of exposure and infection. Am J Ophthalmol. 2015;160:516–521. 8. Einan-Lifshitz A, et al. Repair of exposed Ahmed glaucoma valve tubes: long-term outcomes. J Glaucoma. 2018;27:532–536. 9. Grover DS, et al. Forniceal conjunctival pedicle flap for the treatment of complex glaucoma drainage device tube erosion. JAMA Ophthalmol. 2013;131:662–666. Editors’ note: Dr. Myers is Chief of the Glaucoma Service, Wills Eye Hospital, Philadelphia, Pennsylvania, and has interests with Aerie, Avisi, Allergan, Equinox, Glaukos, Guardion Health Sciences, Haag-Streit, MicroOptx, Nicox, Olleyes, and Santen. Dr. Razeghinejad is Director, Glaucoma Fellowship Program, Wills Eye Hospital, Philadelphia, Pennsylvania, and has interests with Olleyes. Dr. Smith is in practice with Glaucoma Associates of Texas, Dallas, Texas, and has interests with New World Medical. Jaewan Choi, MD, PhD Partner and Director of Glaucoma Service Central Seoul Eye Center Seoul, South Korea ASIA-PACIFIC PERSPECTIVES If there is no risk of re-exposure, I believe that primary repair with or without patch graft is the best surgical option for tube exposure. However, the real world is different. Alawi et al. recently shared their experience with eyes that presented with an initial GDD exposure and the subsequent outcome of primary repair in terms of re-exposure.1 In this study, 18 eyes of 43 eyes had a second re-exposure, and four eyes had a third re-exposure, and 1 eye had a fourth re-exposure. Re-exposure rate was more than 40 percent, which is not negligible. Notably, the usage of patch graft did not completely reduce the possibility of tube re-exposure. Thus, if the risk of re-exposure following primary repair is estimated to be high, a customized approach Is warranted. The risk factors for tube exposure may include too anterior insertion of the tube, previous ocular surface surgery, large area of tube exposure, or severe vascularization of conjunctiva. The simple coverage of patch graft and conjunctiva cannot guarantee the surgical success in these situations, necessitating modified techniques. If the tube insertion is too anterior, the removal of the tube from the original insertion site and creation of a new sclerotomy at a more posterior location could be considered. If the conjunctiva is heavily scarred and stuck to sclera, the primary repair may not be that easy. In eyes with higher risk for surgical failure, single- or double-thickness patch graft over the tube, repositioning of the tube in a different quadrant using a tube extender, or the use of double-layered amniotic membrane may be considered as alternative or fortifying techniques. Autologous serum also may be used to promote epithelial growth.2 In the most refractory cases with recurrent tube erosion, permanent removal of the tube part or the whole GDD combined with a secondary glaucoma surgical procedure should be considered. As secondary surgical procedure, transscleral cyclophotocoagulation (CPC) with MicroPulse laser mode or with slow coagulation continuous wave mode is freµuently selected. However, it is notable that the surgical efficacy may be different between procedures. For example, the MicroPulse laser Î000 mW achieves a less efficient I"P decrease as well as the number of antiglaucoma medications than the Ahmed valve implantation in a study.3 Recently, slow coagulation continuous wave mode CPC using G-probe with 1250 mW power and 4000 ms duration have shown promising efficacy in various clinical settings,4-5 and this technique could be another option in this situation. References 1. Alawi A, et al. Tube revision Outcomes for Exposure with Different Repair Techniques. Clin Ophthalmol. 2020 Oct 2;14:3001-3008. 2. Ainsworth G, et al. A novel use of amniotic membrane in the management of tube exposure following glaucoma tube shunt surgery. Br J Ophthalmol. 2006 Apr;90(4):417–419. 3. Fili S, et al. Transscleral cyclophotocoagulation with Micropulse laser versus Ahmed valve implantation in patients with advanced primary open-angle glaucoma. Int Ophthalmol. 2021 Apr;41(4):1271-1282. 4. Khodeiry at al. Treatment Outcomes of Slow Coagulation Transscleral Cyclophotocoagulation In Pseudophakic Patients with Medically Uncontrolled Glaucoma. Am J Ophthalmol. 2021 Sep;229:90-99. 5. Khodeiry et al. Slow Coagulation Transscleral Cyclophotocoagulation for Postvitrectomy Patients with Silicone Oil-induced Glaucoma. J Glaucoma. 2021 Sep 1;30(9):789-794. ditors½ note\ Dr. hoi declared no relevant financial interests
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