Analysis of lacrimal duct morphology from cone-beam CT dacryocystography in a Japanese population

Abstract Purpose: The dacryoendoscope is a practical instrument for the examination and the treatment of lacrimal duct obstruction. Nevertheless, being a rigid fiberscope, manipulation of the endoscope 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 differ 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: We retrospectively analyzed the CBCT-DCG images of 102 cases diagnosed with unilateral primary acquired nasolacrimal duct obstruction (PANDO) at Ehime University Hospital from December 2015 to May 2021. We investigated the following parameters of the lacrimal duct on the contralateral side of unilateral PANDO: 1) the angle formed by the superior orbital rim–internal common punctum–nasolacrimal duct opening, 2) the angle formed by the lacrimal sac and the nasolacrimal duct, 3) the length of the lacrimal sac, 4) the length of the nasolacrimal duct.Results: The measurement results were as follows: 1) 10.2 ± 7.8° (range, −11° to +27°); 2) −6.3 ± 14.1° (range, −43° to +40°); 3) 8.9 ± 2.3 mm (range, 4.3–17.1); 4) 13.2 ± 2.7 mm (range, 5.7–20.7). Of these parameters, values of all except 3) followed a normal distribution.Conclusions: We reported anthropometric data analyzing 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 inclined anteriorly in 92% of cases. In such cases, a probe with a bent or curved tip was considered more appropriate than a straight-type probe.