To compare the result of mitomycin C (MMC) instillation after silicone intubation in partial nasolacrimal duct obstruction in adults according to duration of instillation.

An instillation of 0.04% MMC eyedrops was performed on 61 eyes of 38 patients diagnosed with partial nasolacrimal duct obstruction. The clinical result of patient groups, classified according to duration of MMC eyedrops instillation, was analyzed prospectively. The patients groups was as follows: no MMC eyedrop instillation (group A), 1 week of MMC instillation (group B), 2 weeks of MMC instillation (group C), and 3 weeks of MMC instillation (group D).

Among all patients, 50 eyes (81.9%) showed improved symptoms. Fifteen eyes (71.4%) in group A, 8 eyes (72.7%) in group B, 13 eyes (86.7%) in group C and 14 eyes (100.0%) in group D had a successful outcome. The success rate was observed in groups D, C, B, and A, in descending order, which was statistically significant ( p = 0.025).

Silicone intubation is an effective treatment option for partial nasolacrimal duct obstruction in adults and MMC eyedrop instillation may improve silicone intubation results.