Quantification of Nasolacrimal Duct Obstruction Length and Its Relationship with Surgical Outcomes

<b>Background/Objectives:</b> Although the outcomes of endoluminal lacrimal duct recanalization (ELDR) for nasolacrimal duct (NLD) obstruction are associated with the obstruction length, NLD obstruction has not been quantified. In this study, we aimed to quantify the obstruction length using a calibrated dacryoendoscope and investigate its relationship with surgical outcomes following endoscopic recanalization of the lacrimal passage. <b>Methods:</b> We retrospectively analyzed the eyes of patients who underwent ELDR using a calibrated dacryoendoscope at our institution between January 2023 and February 2025. Patients with dacryocystitis detected during preoperative irrigation testing were excluded. A lacrimal tube was placed for 2 months after recanalization, and we used the calibrated dacryoendoscope to measure the obstruction length. The 3-month postoperative outcomes were determined using irrigation testing, subjective symptoms, and cotton thread testing. <b>Results:</b> A total of 31 eyes of 26 patients (6 eyes of 5 males; 25 eyes of 21 females; mean age, 68.8 ± 10.5 years) were included in this study. The mean obstruction length was 10.8 mm (range: 1-30 mm). The nasolacrimal duct was patent, showed reflux, and was obstructed in 12, 16, and 3 eyes, respectively, at 3 months. The symptoms resolved, improved, and remained unchanged in 18, 11, and 2 eyes, respectively. Trend analysis revealed a significant relationship between the obstruction length and irrigation outcomes. However, no significant association was observed with the symptoms. The obstruction length was significantly correlated with the 3-month postoperative cotton thread test results. <b>Conclusions:</b> The NLD obstruction length was associated with the 3-month postoperative irrigation test results, and longer obstruction was associated with poorer postoperative outcomes.