Impact of glaucoma medications on subsequent Schlemm's canal surgery outcome: Cox proportional hazard model and propensity score-matched analysis

Purpose: The impact of various preoperative glaucoma medications on Schlemm's canal surgery outcomes remains unclear. This study aimed to investigate the impact of preoperative glaucoma medications on the postoperative 1-year outcomes of mu TLO. Methods: We analyzed the medical records of 218 patients who underwent their first mu TLO to investigate the 1-year postoperative outcomes. Cox proportional hazard regression analysis was performed with surgical failure as the dependent variable and each type of preoperative medication as the independent variable. We also compared the 1-year outcomes of mu TLO between users and non-users of specific medications using propensity score matching. Surgical success was defined as a postoperative intraocular pressure ranging from 5 to 21 mmHg, a >= 20% reduction in IOP from baseline, and no additional glaucoma surgery within 1 year postoperatively. Results: The Cox proportional hazard analysis showed that all drugs that do not increase the conventional outflow exhibited hazard ratios greater than 1.0, and the preoperative use of beta-blockers and oral CAI was a significant surgical risk factor (hazard ratio: 2.65 and 2.45, p = 0.04 and <0.001). In the propensity score matching analysis, success rates at 1 year postoperatively were 55/85, 54/79, 60/73, and 40/76% for users/non-users of beta-blockers, topical CAIs, an alpha-2 adrenergic agonist, and an oral CAI, respectively. Kaplan-Meier survival curves in these comparisons also demonstrated that preoperative beta-blockers and oral CAI use were significant surgical risks (p = 0.01, <0.001). Conclusion: Our study suggests that preoperative medications that do not involve conventional pathway outflow have a detrimental effect on subsequent Schlemm's canal surgery outcomes.