Multidetector CT of Nasolacrimal Canal Morphology: Normal Variation by Age, Gender, and Race

Purpose: To accurately characterize anatomical age, gender, and racial differences in normal nasolacrimal canal morphology and to describe a new, accurate technique for measuring nasolacrimal canal parameters based on high-resolution CT. Methods: The CT images of 72 patients were reviewed retrospectively and grouped according to age, gender, and race. Patients with history of long-term sinusitis, facial trauma, or nasolacrimal duct pathology were excluded from study. Variations in nasolacrimal duct length, minimal and maximal diameter, and other metrics were recorded and compared across each category. All patient records were deidentified to protect privacy. Results: Nasolacrimal canal length and volume were significantly greater in men than those in women. A trend was noted for greater canal cross-sectional diameter in patients older than 50 years when compared with that in younger patients. Significant differences in canal diameters were noted at the canal apex and base of older patients compared with those of younger patients. The cross-sectional area of the canal base was greater in black patients than that in Caucasian patients. Conclusions: Although some significant age, gender, and racial variations of nasolacrimal canal morphology exist, these do not fully explain the epidemiology of primary acquired nasolacrimal duct obstruction. The new method described here for measuring nasolacrimal canal metrics is straightforward and theoretically more accurate than those previously defined in the literature.