Précis: The Preserflo Microshunt (PSM) is a safe and effective glaucoma microfiltering implant that significantly reduces the intraocular pressure (IOP), either alone or in combination with phacoemulsification, during the first year after surgery. Purpose:The purpose of this study was to assess the safety and efficacy of the PSM for the treatment of open angle glaucoma with 0.2 mg/mL mitomycin C, either alone or in combination with cataract surgery. Methods:A retrospective, open-label study of 64 eyes with primary open angle glaucoma that underwent PSM implantation and were followed up for at least 9 months. Success was defined as IOP 6-17 mm Hg and a reduction of at least 20%, complete without hypotensive medication, and qualified with medication. Safety was assessed by the incidence of adverse events. Secondary endpoints included mean hypotensive medications, visual acuity, and incidence of needling and surgical revision.Results: A total of 51 eyes underwent PSM alone and 13 underwent PSM+phacoemulsification. In the overall population of the study, the mean IOP was significantly reduced from 22.03 ± 0.7 mm Hg at baseline to 12.7 ± 0.4 mm Hg at the final visit, P < 0.0001 (mean follow-up: 11 ± 1.4 mo). The IOP was significantly reduced in both groups (P < 0.0001). Ocular hypotensive medication was reduced significantly from 2.7 ± 0.7 to 0.2 ± 0.5 (P < 0.0001). No significant differences were found in IOP-lowering medication between groups (PSM alone, 0.2 ± 0.08; PSM+phacoemulsification, 0.1 ± 0.1; P = 0.2). At the final visit, 70.3% were considered as complete success and 12.5% as qualified success. The most common adverse event was clinical hypotony (7.8%) followed by hyphema (4.7%), and anterior chamber reformation (1.6%). Overall, 1.6% required needling and 15.6% surgical revision to restore the flow. Conclusion:Glaucoma surgery with the PSM and mitomycin C was efficacious and safe in the short term, either alone or in combination with cataract surgery, and may be considered a surgical option for lowering IOP in primary open angle glaucoma.