A Case of Delayed-Onset Hyphema After PreserFlo MicroShunt Implantation

We report a case of delayed-onset hyphema with reflux bleeding adjacent to the PreserFlo MicroShunt (PFM) tube entry site. A 66-year-old Japanese man with bilateral primary open-angle glaucoma underwent PFM implantation in the left eye because of elevated intraocular pressure (IOP) and progressive visual field loss despite treatment with four topical anti-glaucoma agents. He had previously undergone cataract surgery and microhook ab interno trabeculotomy (μLOT) in the same eye. Because of insufficient IOP control and further visual field progression after PFM implantation, Ahmed glaucoma valve implantation with pars plana tube insertion was subsequently performed in combination with 25-gauge pars plana vitrectomy. At two years and three months after PFM implantation, a small number of red blood cells were observed floating in the anterior chamber. Gonioscopy showed that the PFM tube was positioned between the pigmented and non-pigmented trabecular meshwork, with reflux bleeding from both sides of the tube entry site. The previous μLOT clefts did not overlap with the PFM tube entry site. The hyphema resolved with observation alone, although possible recurrence was noted six months later. This case demonstrates that delayed-onset hyphema can occur more than two years after PFM implantation and that careful gonioscopic examination can help identify the source of bleeding.