Objectives/Hypothesis: To evaluate the efficacy of intraoperative mitomycin C (MMC) in endonasal endoscopic dacryocystorhinostomy.

Study Design: Randomized controlled trial.

Methods: Fifty patients with primary acquired nasolacrimal duct obstruction were enrolled and randomly allocated into the treatment and control group. The patients underwent standard endonasal endoscopic dacryocystorhinostomy with mucosal flaps and mitomycin C or placebo on each group. The ostium size was measured at 3 months, 6 months, and 12 months to evaluate the effect of mitomycin C and placebo, and the patency of the lacrimal drainage system was assessed.

Results: There was no statistical significance in the success rate between the MMC group and the control group at 1-year follow-up (84.6% vs.79.2%, respectively, P = .59). At the 6-month and 12-month visits, the mean ostium size in the MMC group was 10.8 mm² (SD = 3.17) and 3.0 mm² (SD = 1.78), respectively, which were prominently larger than the control group at 7.1 mm² (SD = 2.62; P < .001, 95% CI, 0.84–5.45) and 1.6 mm² (SD = 1.18; P = .004, 95% CI, 0.49–2.38).

Conclusions: There was no statistically significant difference in the success rates of both groups, but MMC seems to have a conspicuous effect on the healing process at the ostium.