Eyeworld

61 EW RESIDENTS January 2018 as minimally invasive filtration surgery" While the results are intriguing, there are several limitations to the study. The sample size is relatively small, and the short follow-up peri- od of 12 months restricts the extent of conclusions that can be drawn. As would be expected with any glaucoma surgery, length of efficacy is essential to assessing its value; we would hope that the IOP-lowering effects of the discussed interven- tion are longstanding, but this is unknown with the current data. Pre- sentation of results using prospec- tively defined success and failure criteria would be helpful, as has been advocated by the World Glau- coma Association in its Guidelines on Design and Reporting of Glaucoma Sur- gical Trials. 10 Such definitions would allow for a rudimentary survival analysis, albeit the follow-up period of this study is relatively short. Two distinct cohorts are present in the study: those who received concurrent cataract surgery with iStent insertion and those who received iStent insertion only. As was discussed by the authors, cataract surgery is known to have an IOP-lowering effect. Notably, elevated preoperative IOP, as these patients had, is correlated with a large postoperative IOP decrease. 11 These patients essentially under- went two interventions that could have provided IOP reduction and hence deserve a separate subgroup analysis. Perhaps a cataract ex- traction-only group could have been identified and utilized as a control group, although their preoperative IOP would likely have been lower than the study group. It also would have been useful to compare this novel approach in advanced glau- coma with the current standard of care for refractory glaucoma (i.e., repeat trabeculectomy or tube shunt surgery). A table summarizing the baseline demographic and ocular characteristics of the study popu- lation would have been helpful. Elapsed time between the last prior filtration surgery and the current intervention would be information of interest to readers. We were surprised to see no statistical analyses when reviewing the results. Student's t-test analyses would be essential in demonstrating statistical significance regarding the decrease in IOP and number of med- ications. No intraoperative or post- operative complications were seen in the study. However, it would have been useful to know what specific complications were tracked. A signif- icant percentage (36%) of patients required additional surgery after the intervention, yet no additional information regarding this subset of patients was provided. What was the mean time to failure in this group? A Kaplan-Meier survival curve would be useful here. Were these patients included in the final analysis? Perus- al of Figures 2 and 3 in the journal article shows only 25 data points cumulatively, yet the sample size consists of 42 eyes. It is unclear from the text why a portion of the study eyes was not included in this graph. We applaud the authors for a novel hypothesis regarding the utility of angle surgery in advanced glaucoma patients who have failed filtration surgery and for conducting this initial assessment. This possi- bility is one that deserves further consideration after the study's find- ings, given the limited options that currently exist in the management of refractory, severe glaucoma. EW References 1. Saheb H, et al. Micro-invasive glaucoma surgery: current perspectives and future di- rections. Curr Opin Ophthalmol. 2012;23:96– 104. 2. Richter GM, et al. Minimally invasive glau- coma surgery: current status and future pros- pects. Clin Ophthalmol. 2016;10:189–206. 3. Gedde SJ, et al. Postoperative complica- tions in the Tube Versus Trabeculectomy (TVT) study during five years of follow-up. Am J Ophthalmol. 2012;153:804–814. 4. Gedde SJ, et al. The Tube Versus Trabe- culectomy Study: Interpretation of results and application to clinical practice. Curr Opin Ophthalmol. 2012;23:118–26. 5. Lavia C, et al. Minimally-invasive glaucoma surgeries (MIGS) for open angle glaucoma: A systematic review and meta-analysis. PloS One. 2017;12:e0183142. 6. Resende AF, et al. IStent trabecular microbypass stent: An update. J Ophthalmol. 2016;2016:2731856. 7. Samuelson TW, et al. Randomized evalua- tion of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology. 2011;118:459– 67. 8. Katz LJ, et al. Prospective randomized study of one, two, or three trabecular bypass stents in open-angle glaucoma subjects on topical hypotensive medication. Clin Ophthalmol. 2015;9:2313–20. 9. Chang DF, et al. Efficacy of two trabec- ular micro-bypass stents combined with topical travoprost in open-angle glaucoma not controlled on two preoperative medi- cations: 3-year follow-up. Clin Ophthalmol. 2017;11:523–528. 10. Heuer DK, et al. Consensus on definitions of success. In: Shaarawy TM, Sherwood MB, Grehn F, eds. Guidelines on Design and Re- porting of Glaucoma Surgical Trials. Amster- dam, the Netherlands: Kugler. 2008:15–24. 11. Slabaugh MA, et al. The effect of phacoemulsification on intraocular pressure in medically controlled open-angle glaucoma patients. Am J Ophthalmol. 2014;157:26–31. Contact information Gedde: sgedde@med.miami.edu Trabecular micro-bypass stents as minimally invasive approach after conventional glaucoma filtration surgery – a retrospective analysis since 2014 Thomas Macher, MD, Heike Häberle, MD, Juliane Wächter MD, Carsten Thannhäuser, MD, Henning Aurich, MD, Duy-Thoai Pham, MD J Cataract Refract Surg. 2018;44(1). Article in press. Purpose: To evaluate long-term efficacy and safety of two trabecular micro-bypass stents in patients with advanced primary open angle glaucoma (POAG) and insufficient intraocular pressure (IOP) after previous filtration surgery. Setting: Vivantes Klinikum Neukölln, Augenklinik, Berlin, Germany Design: Retrospective, single-center, open-label, non-randomized study Methods: 42 eyes with uncontrolled and advanced POAG since 2014 were analyzed. All eyes had previously undergone at least one filtration surgery procedure. The anatomical landmarks and configuration of the anterior chamber angle had to be identified easily. Two iStents were placed nasal into Schlemm's canal. Results: 18 of 42 eyes had one previous glaucoma filtration surgery before. During the follow-up of 12 months mean IOP in cases of primary failure of filtration surgery decreased from preoperative 23.8 (±3.9) mm Hg to 15.2 (±2.7) mm Hg. For cases with more than one previous filtration surgery mean IOP decreased from preoperative 26.1 (±5.7) mm Hg to 16.3 (±3.3) mm Hg. Medications were reduced from 2.7 (±0.9) to 2.0 (±1.1). No intraoperative or perioperative complications occurred. Conclusions: For eyes with previous filtration surgery and medically uncontrolled IOP the implantation of two iStent inject provided a minimally invasive and safe reduction of mean IOP to <18 mm Hg at 12 months. Number of medications could be reduced to improve adherence.

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