Analysis of Lacrimal Duct Morphology from Cone-Beam Computed Tomography Dacryocystography in a Japanese Population

Purpose: The dacryoendoscope is a practical instrument for the examination and the treatment of lacrimal duct obstruction. Nevertheless, as it is a rigid fiberscope, manipulation of the endo scope is somewhat affected by the patient's lacrimal duct alignment and the skeletal structure of the face. The morphology and inclination of the lacrimal duct vary among individuals and ethnic groups. We aimed to evaluate the alignment of the lacrimal duct from the perspective of endoscopic maneuverability in a Japanese population. Methods: This retrospective study analyzed the cone-beam computed tomography dacryocystography (CBCT-DCG) images of 102 patients diagnosed with unilateral primary acquired nasolacrimal duct obstruction (PANDO) at Ehime University Hospital from December 2015 to May 2021. The following parameters of the lacrimal duct on the contralateral side of unilateral PANDO were investigated: (1) angle formed by the superior orbital rim-internal common punctum-nasolacrimal duct opening, (2) angle formed by the lacrimal sac and the nasolacrimal duct, (3) length of the lacrimal sac, and (4) length of the nasolacrimal duct. Results: Measurements of the above parameters were (1) 10.2 degrees +/- 7.8 degrees (range, -11 degrees to +27 degrees), (2) -6.3 degrees +/- 14.1 degrees (range, -43 degrees to +40 degrees), (3) 8.9 +/- 2.3 mm (range, 4.3-17.1), and (4) 13.2 +/- 2.7 mm (range, 5.7-20.7), respectively. The Shapiro-Wilk test demonstrated that the values of all parameters, except (3), followed a normal distribution (p = 0.55, 0.30, 0.0002, and 0.39, respectively). No significant difference was found between the female and male groups (p > 0.05). Conclusion: This study reported anthropometric analysis data of the morphology of the lacrimal ducts using CBCT-DCG in a Japanese population. In our cohort, the line from the superior orbital rim through the internal common punctum to the nasolacrimal duct opening inclined anteriorly in 92% of the patients.