3D morphometric study of the nasolacrimal duct and its implication in recanalization of nasolacrimal duct obstruction.

Purposes: The nasolacrimal recanalization, consisting of retrograde removal of obstructing tissues using electrocauterization, is an evolutionally developed surgical procedure to treat the nasolacrimal duct (NLD) obstruction. To perform the nasolacrimal recanalization requires an understanding of three‐dimensional (3D) structure of the NLD, but very few data are available about its stereotactic shape. This study aims at investigating the anatomy of the NLD through 3D visualization and metric assessment of 3D models obtained from the cranial CT‐scans. Methods: This study included 20 males and 20 females (range: 18–68 years), who underwent autopsy at the National Forensic Service Seoul Institute, Seoul, Korea. Post‐mortem cranial CT‐scans were achieved in helical mode with slice thickness of 0.75 mm and 120 kV. 3D models of the NLD were reconstructed from serial CT slices after performing semi‐automated segmentation by tracing and filling the outline of the nasolacrimal duct by Mimics software (version 20.0, Materialise, Leuven, Belgium). Results: Overall length of NLD, anteroposterior and transverse entrance diameters of bony NLD (BNLD), and lacrimal sac‐BNLD angle was significantly higher in males than females. Compared with right and left, most variables showed no significant differences in statistics, except for lacrimal sac‐BNLD angle. BNLD orientation type in coronal plane showed outward type than inward by over 80%. Collectively, the whole appearance of the NLD was shaped like a bowleg in which the distal part is relatively turned inward. Conclusion: These results suggest that 3D models of the NLD were crucial for understanding structural recognition, mainly related to model‐based image analysis, and useful to aid in the surgical procedure and treatment of the nasolacrimal duct obstruction. The authors wish to acknowledge the financial support of the Catholic Medical Center Research Foundation made in the program year of 2019 (No. 552019B000100003). [ABSTRACT FROM AUTHOR]