Diabetes Mellitus: A Risk Factor in Schlemm's Canal-Based Minimally Invasive Glaucoma Surgery

Objectives: The objective of this study was to evaluate the impact of diabetes mellitus (DM) on the outcome of Schlemm's canal-based minimally invasive glaucoma surgery (MIGS). Methods: In a retrospective interventional cohort study, postoperative intraocular pressure (IOP) and intracameral bleeding were analyzed in 25 diabetic patients and 84 non-diabetic patients, with primary open-angle glaucoma (POAG) or ocular hypertension (OH). Results: The mean follow-up period for all 109 eyes was 35.3 ± 24.8 months. There was no significant difference in preoperative IOP between cohorts with or without diabetes. However, the post-surgical IOP between 3 months and 2 years was significantly higher in the cohort with diabetes (p = 0.019 to 0.001). The 3-year survival probability of achieving an IOP ≤ 15 mmHg was 17.8 ± 0.09% in patients with diabetes, significantly lower than the 30.4 ± 0.06% observed in patients without diabetes (p = 0.042 Log-rank test). The 3-year survival probability of achieving an IOP ≤ 18 mmHg was 56.7 ± 0.12% in patients with diabetes compared to 79.5 ± 0.05% in patients without diabetes, indicating a marginally significant difference between cohorts with and without diabetes (p = 0.065). When the random effect of diabetes mellitus (DM) was analyzed alongside the fixed effects of preoperative IOP, age, refractive error, and the extent of canal opening using a multivariate linear mixed model, DM emerged as a significant risk factor for higher postoperative IOP at both 6 and 12 months (p < 0.001). Conclusions: Diabetes mellitus is a significant risk factor for poor outcomes following Schlemm's canal-based MIGS, particularly in achieving lower postoperative IOP.