Preserflo MicroShunt Outcomes in Rare and Refractory Glaucoma Entities Compared with Matched Primary Open-Angle Glaucoma Controls: A Retrospective Exploratory Study.

PURPOSE: To investigate the efficacy and safety of the Preserflo MicroShunt (PMS) in rare and refractory glaucoma entities (RRG) in comparison with primary open-angle glaucoma (POAG). PATIENTS AND METHODS: In this retrospective exploratory study, the primary outcome was the complete 1-year success rate (≥20% reduction in IOP from baseline and ≤18 mmHg with no medication use). Kaplan-Meier estimates were compared between RRG and POAG (matched 1:1) using the log-rank test. Exploratory sub-analyses were performed for each RRG subgroup. The secondary outcomes included bleb revision and complication rates. RESULTS: Eighty eyes were included in the RRG group (8 primary congenital (PCG), 11 juvenile open-angle (JOAG), 10 aphakic (AG), 14 combined mechanisms (CMG), 17 neovascular (NVG), 13 post-traumatic (TG), 4 oil-induced, 2 steroid-induced glaucoma, and 1 with idiopathically elevated episcleral venous pressure) and matched to 80 eyes with POAG based on baseline characteristics. The 1-year success rates were 56% in the RRG and 71% in the POAG groups (p = 0.0079). Exploratory subgroup analyses revealed significantly lower success in PCG (2/8), TG (8/13) and NVG (8/17). Success rates in the other groups were not significantly different from POAG. Bleb revisions were required significantly more frequently in the RRG group (58% vs 41%). Severe complications were observed in the RRG group, but did not reach significance. CONCLUSIONS: While the PMS demonstrated lower efficacy in RRG compared to POAG overall, this difference was primarily attributable to worse outcomes in NVG, TG, and PCG. Success rates in AG, JOAG, and CMG were not significantly different from POAG controls. The frequent need for postoperative bleb revisions, particularly in NVG, PCG, and TG subgroups, represents an important practical consideration. Given the small subgroup sizes and exploratory design, these findings warrant validation in larger, prospective studies.