PreserFlo MicroShunt Outcomes in Asia: Two-Year Results with Exploratory Comparisons of Standalone and Combined Surgery from a Regional Tertiary Centre

Background/Objectives: To evaluate the two-year efficacy and safety of PreserFlo MicroShunt (PMS) implantation in an Asian cohort with primary open-angle glaucoma via post hoc exploratory comparison of standalone PMS versus combined phacoemulsification and PMS (PMS+Phaco). Methods: This prospective single-centre cohort study included 30 consecutive eyes of 30 patients who underwent PMS implantation and were followed for 24 months. Nine eyes underwent standalone PMS and 21 underwent PMS+Phaco. The primary outcome was surgical success assessed using Kaplan–Meier survival analysis. Qualified success was defined as intraocular pressure (IOP) of 6–21 mmHg with ≥20% reduction from baseline, with or without IOP-lowering medication; complete success required no glaucoma medications. Failure was defined as not meeting success criteria at two consecutive visits, with the earliest failure at 3 months. WGA-style definitions were retained to ensure comparison with the published literature. Results: Median age was 73 years (IQR 70–78), baseline IOP was 16.0 mmHg (14.0–18.4), and patients were using a median of 3 (2–3) IOP-lowering medications. At 24 months, median IOP was 15.0 mmHg (13.0–17.1), with 57% of eyes remaining medication-free. Whole-cohort qualified success at 24 months was 36.7% (95% CI 20.1–53.4). Qualified success was 44.4% (95% CI 13.6–71.9) for standalone PMS and 33.3% (14.9–53.1) for PMS+Phaco (log-rank p = 0.586). Using alternative IOP thresholds, 83.2% of eyes achieved qualified success at IOP < 18 mmHg and 76.5% did so below the cohort baseline mean of 16.5 mmHg. Corneal oedema was more frequent after combined surgery (38.1% vs. 0%). Bleb needling was required in 40% of eyes. Conclusions: PMS implantation, performed alone or with phacoemulsification, was associated with sustained reduction in medication burden, with 57% of eyes remaining medication-free at 24 months. Absolute IOP control over 24 months was modest. In post hoc exploratory analysis, no difference in surgical success was detected between procedural approaches; however, confidence intervals were wide and data were insufficient to establish equivalence. Low success rates using conventional criteria likely reflect the cohort’s relatively low baseline IOP (median 16.0 mmHg).