Aim To investigate the incidence of late onset bleb-related infection (BRI) following Mitomycin C (MMC) augmented trabeculectomy procedures at a single institution.

Methods This was a retrospective case series analysis of late onset BRI, defined as either blebitis or endophthalmitis occurring at least 1 month following a glaucoma filtration procedure. Data collected from hospital charts included the position of the conjunctival flap base. Two cohorts were examined: the first a sample of 194 intraoperative MMC augmented trabeculectomies undertaken over a 4-year period from 1993 to 1997, and the second a sample of 764 MMC trabeculectomies performed in a 4-year period between the years 1999 and 2005.

Results A total of 11 cases of BRI (cumulative incidence 5.7%) were identified in the cohort from 1993 to 1997. BRI cases had trabeculectomies performed with a limbus-based conjunctival flap and presented at a median IQR 14.8 (9.4–42.9) months after surgery. In the 1999–2005 cohort, nine cases of BRI were identified (cumulative incidence 1.2%). All these BRI cases had a fornix-based conjunctival flap and presented at a median IQR 19.2 (6.1–44.1) months after trabeculectomy surgery.

Conclusion This study found that the incidence of BRI was higher in MMC augmented trabeculectomy shortly after the introduction of MMC, but subsequently reduced to a lower level. While many changes in surgical technique had occurred in the intervening period, the most significant change was from limbus-based to fornix-based conjunctival flap. However, the retrospective nature of the study prevents the authors from concluding that there is a causative relationship between changes in surgical technique and BRI.