To evaluate the obstruction nature on success rate of monocanalicular nasolacrimal duct intubation in congenital nasolacrimal duct obstruction. Congenital Nasolacrimal Duct Obstruction (CNLDO) is a common finding in childhood and is the most frequent cause of chronic epiphora in children. It results from uncanalization of distal portion of nasolacrimal duct called 'Hasner valve'.

In a clinical trial study 96 eyes of 88 children in two groups including patients <24 months with failed probing history and patients ≥24 months without failed probing history were investigated. Tube removal was planned for 3 months postoperatively. Treatment success was defined as no epiphora or mucus discharge at 3 months after probing.

The mean age at the time of intubation was 35.45±14.70 months.(range: 16-85 months). Treatment success was achieved in 89 of 96 eyes (92.7% ). Simple obstruction was found in 58 of 96 eyes(60%) and complex obstruction was found in 41 of 96eyes(40%). The success rate was nearly the same in two groups(p=0.401). In the group < 24 months success rate after 6 months was 88.2 % and in the group ≥24 months that was 93.7 %. Fisher exact test did not show any significant association between age groups and success rate after 6 months of following(p=0.360). 91.3 % of primary probing had successful intubation versus 94.7 % of secondary probing. There was not significant relation between probing history and success rate after 6 months of following(p=0.425).

According to our findings, age and obstruction nature do not have any effect on success rate of primary monocanalicular nasolacrimal duct intubation in congenital nasolacrimal duct obstruction. So they cannot be considered as predictive factors for success rate in monocanalicular nasolacrimal duct intubation.