Intranasal Mometasone After External Dacryocystorhinostomy—Necessity or Convention? A Retrospective Two-Centre Cohort Study

Background/Objectives: Intranasal corticosteroids are frequently prescribed after dacryocystorhinostomy (DCR) to modulate mucosal healing and prevent ostium closure, but evidence supporting their use after external DCR (EXT-DCR) is scarce. This study compared early anatomical success after EXT-DCR under two centre-specific postoperative protocols that differed in the use of intranasal mometasone. Methods: Retrospective comparative cohort study of 243 consecutive EXT-DCR procedures (211 patients) for distal lacrimal obstruction performed by a single surgeon using the same technique at two centres between 2019 and 2025. Postoperative treatment was determined by each centre’s standing protocol: both included oral amoxicillin–clavulanic acid for one week, and one centre additionally prescribed intranasal mometasone furoate twice daily for two months (mometasone group, n = 64; control group, n = 179). The primary outcome was anatomical success, defined as lacrimal patency on irrigation at two months. Groups were compared with Fisher’s exact test and a multivariable logistic regression adjusted for age and sex. Results: Anatomical success was 93.8% (60/64) in the mometasone group and 89.9% (161/179) in the control group (absolute difference 3.8 percentage points; 95% CI −5.7 to 10.3; p = 0.45). After adjustment for age and sex, treatment group was not significantly associated with success (control vs. mometasone: OR 0.57; 95% CI 0.18–1.77; p = 0.33). No statistically significant associations were detected for age or sex. Conclusions: In this cohort, adding a two-month course of intranasal mometasone to standard postoperative care after EXT-DCR was not associated with a statistically significant improvement in early anatomical success. Given the limited statistical power and a confidence interval that does not exclude a clinically meaningful benefit, this absence of a significant difference does not establish therapeutic equivalence. Adequately powered prospective trials with longer follow-up are needed before routine intranasal corticosteroid use after EXT-DCR can be either recommended or abandoned.