An anatomical basis for primary acquired nasolacrimal duct obstruction.

Objective: To measure any sex size differences in the bony nasolacrimal drainage systems in a normal, age-matched population.
Methods: A retrospective study of axial cut maxillofacial computed tomographic scans was conducted. Three levels of the bony nasolacrimal duct (NLD) system on the right and left sides were measured along the anteroposterior diameter. The data were analyzed using 2-tail t test, analysis of variance, and linear regression methods.
Results: Scans from 71 adult patients (36 men and 35 women) were reviewed. Women were found to have a smaller bony diameter at the level of the lower fossa (P = .01) and the middle NLD (P = .06) compared with those of men. The adult inferior bony fossa increased in size with age in both men and women, while the middle NLD increased in size in men only. No significant size difference was found between the right and left side at any level.
Conclusions: Size differences are found in measurements of bony nasolacrimal excretory systems in men vs women. Women have significantly smaller dimensions in the lower nasolacrimal fossa and the middle NLD. The anteroposterior dimension of the bony nasolacrimal canal at the fossa level enlarged in both sexes, with age co-inciding with osteoporotic changes throughout the body. These quantitative anatomical observations provide a contributory factor to explain the increased prevalence of primary acquired NLD obstruction in women.