Objectives: To determine the diameters of the bony nasolacrimal canal and to evaluate how they are affected by sex and age.
Methods: Standard axial sinus computed tomographic images of 314 patients were assessed retrospectively; the anteroposterior and transverse diameters, the sectional area of the bony nasolacrimal canal at the level of the infraorbital margin, and the angle between the bony canal and the nasal floor were measured.
Results: The mean results were as follows: anteroposterior diameter, 5.6 mm; transverse diameter, 5.0 mm; sectional area of the bony nasolacrimal canal, 22.6 mm(2); and angle between the bony canal and the nasal floor, 78.3 degrees . Females had a significantly smaller anteroposterior diameter (mean 0.6 mm) and a significantly smaller transverse diameter (mean 0.3 mm). The sectional area of the bony nasolacrimal canal was 13% smaller in females (P < .001). The angle between the bony canal and the nasal floor was a mean of 1.1 degrees more obtuse in males (P = .004). With age, the transverse diameter, the sectional area of the bony nasolacrimal canal, and the angle between the bony canal and the nasal floor in males, and the anteroposterior diameter, the sectional area of the bony nasolacrimal canal, and the angle between the bony canal and the nasal floor in females increased significantly.
Conclusions: In females, the narrowness of the bony nasolacrimal canal and the acute angle between the bony canal and the nasal floor predispose to chronic inflammation of the nasolacrimal drainage system. The results of this quantitative anatomical study may explain why primary acquired nasolacrimal duct obstruction is more frequent in younger female patients.