Factors Associated With Unqualified Success After Trabecular Bypass Surgery: A Case-control Study

Precis: An older age, a low number of baseline glaucoma medications, an early glaucoma stage, lower intraocular pressure (IOP) values during the first postoperative month, and combined surgery are possible predictors of unqualified success after a trabecular by-pass microinvasive glaucoma surgery (MIGS) procedure. Purpose: The purpose of this study was to identify the potential predictors of unqualified success (IOP<18 mm Hg with no glaucoma medication) after trabecular by-pass MIGS. Materials and Methods: We designed a case-control study using logistic regression modeling that included all trabecular by-pass surgeries with at least 3 months of follow-up, performed at a single center from June 2017 to December 2019. Eyes that achieved an endpoint of unqualified success (dependent variable) were considered cases. All other eyes were used as the controls. Cases and controls were paired by sex and postoperative time. We tested the following independent variables: age, race, laterality (right eye or left eye), glaucoma stage, type of surgery (combined or stand-alone), type of trabecular bypass, intraoperative complications, baseline number of medications, baseline IOP, and postoperative IOP on days 1, 15, and 30. Additional analysis using IOP <15 mm Hg as a threshold and including eyes with at least 12 months of follow-up were performed. Results: One hundred ninety-four eyes were included in the analysis. We observed complete success in 56.7% of eyes. The mean follow-up time for the entire population was 12.3±6.8 months. All variables were considered in the first step of the modeling process; however, only age, day-15 IOP, day-30 IOP, baseline number of medications, glaucoma stage, and type of surgery remained until the completion of our model, with adequate significance (P<0.05). The additional analysis confirmed our results. Conclusion: We identified that an older age, a low number of baseline glaucoma medications, an early glaucoma stage, lower IOP values during the first postoperative month, and combined surgery were associated with a higher chance of unqualified success at 12 months after a trabecular by-pass MIGS procedure.