PURPOSE: To report on five-year results with the PreserFlo MicroShunt (MicroShunt) for the surgical treatment of open-angle glaucoma. PATIENTS AND METHODS: Retrospective case series of consecutive patients who underwent a stand-alone MicroShunt implantation at the University Eye Clinic of Maastricht. If a patient underwent the procedure in both eyes, only the first eye was included in the analysis. MicroShunt implantation was augmented with 0.2 mg/ml mitomycin-C. The primary outcome was intraocular pressure (IOP) during follow-up. Furthermore, information on IOP-lowering medication use, success rates, reoperation rates, and postoperative complications was collected. RESULTS: Sixty-six eyes were included for analyses. Diagnoses included primary open-angle glaucoma (88%) and pigmentary glaucoma (12%). The majority of patients had moderate or advanced glaucoma, based on the mean deviation of the visual field examination. Mean (95% - confidence interval) IOP dropped from 21.8 (20.8-22.8) at baseline to 13.2 (11.8-14.6) mmHg after 5 years (p <
0.001). Mean number of IOP-lowering medications was reduced from 2.5 (2.2-2.9) at baseline to 0.9 (0.5-1.2), 1.0 (0.7-1.4), and 1.1 (0.7-1.5) after three, four, and five years (all p <
0.001). Needling or surgical revision was performed in twelve eyes (18%). Nineteen eyes (29%) required further IOP-lowering surgery. Postoperative complications were usually mild and self-limiting and included early hypotony, shallow anterior chamber, and hyphaema. CONCLUSIONS: After five years, the MicroShunt was found to be a safe procedure, leading to a sustained reduction in mean IOP and number of IOP-lowering medications. However, almost one third of the eyes required further IOP-lowering interventions.