Comparison of the efficacies of 1.0mm and 1.5mm silicone tubes for the treatment of nasolacrimal duct obstruction

Purpose: We compared the difference in postoperative patency rates due to the differences in the diameter of silicone tubes used for bicanalicular intubation for the treatment of nasolacrimal duct obstruction (NLDO). Methods: Patients diagnosed with NLDO at Ehime University Hospital between August 2013 and November 2020 who underwent endoscopic-assisted nasolacrimal duct intubation (ENDI) were included in the study. The patients involved were 130 cases and 157 sides (age 72.6 ± 11.3 years) who were eligible for follow-up for more than six months after the removal of the lacrimal silicone tube. The postoperative recurrence rate was compared retrospectively based on the difference in tube caliber. The patients were divided into two groups: those intubated with a 1.5-mm large diameter tube (Group LD) and those with a 1.0-mm normal diameter tube (Group ND). The survival rates of the two groups at one year after tube removal were compared by Kaplan-Meier's curve and Restricted mean survival time (RMST) method with τ = 365 days. Results: There were no significant differences in age, gender, or observation period after tube removal between the two groups. Meanwhile, the preoperative occlusion period was significantly longer in the ND group. The recurrence rate after tube removal was significantly lower in the LD group (12 / 85 sides, 14.1%) compared to the ND group (27 / 72 sides, 37.5%) (p = 0.001). The patency rate at one year after removal of the lacrimal tube was 0.857 (0.754-0.919) in the LD group and 0.739 (0.617-0.828) in the ND group. In comparing patency rates by the RMST method at τ = 365 days, the RMST difference, RMST ratio, and RMTL ratio were significantly higher in the LD group at p = 0.045, 0.052, and 0.046, respectively. Conclusion: Regarding the bicanalicular silicone tube intubation, the patency rate at one year after removal was significantly higher in the thicker tubes with a diameter of 1.5 mm compared with that of a diameter of 1.0 mm for the treatment of NLDO.