Despite an obvious interest in the processes occurring in the lacrimal passages in their obstruction, there is few articles analyzing their biometric parameters.
PURPOSE
The study investigates the biometric characteristics of the lacrimal passages in healthy individuals and in patients with nasolacrimal duct obstruction.
MATERIAL AND METHODS
The study included 81 cases of partial nasolacrimal duct obstruction and 38 cases without tear drainage insufficiency. All patients underwent computed tomography with dacryocystography. Analysis of the biometric parameters involved calculation of the length, volume, and average sectional area of the nasolacrimal duct and the nasolacrimal bony canal. The ratio R4/16l was calculated (where R is the radius of the nasolacrimal duct; l is the length of the nasolacrimal duct). The normality of values was assessed using the Shapiro-Wilk test. Intergroup differences were assessed using the Mann-Whitney test and t-statistics for independent samples. Correlation analysis was performed according to the Spearman method. ROC analysis was carried out. Differences were considered significant at p≤0.05.
RESULTS
There were significant differences in the volume (p=0.004) and the average sectional area of the nasolacrimal duct (p=0.014), as well as in the length of the nasolacrimal canal (p=0.034). Relationships were established between the age of patients without tear drainage insufficiency and the length of the nasolacrimal canal (p=0.042); the length of the nasolacrimal canal and the volume of the nasolacrimal duct (p=0.034), as well as the volume of the nasolacrimal duct and the nasolacrimal canal in partial nasolacrimal duct obstruction (p=0.017). The AUC of the R4/16l ratio in the ROC analysis was 0.653 (p=0.007).
CONCLUSION
In addition to the obvious differences, it was found that the length of the nasolacrimal bony canal significantly differed in the subjects of both study groups. We considered the tear ducts as a hydrodynamic system obeying Poiseuille’s law, so we calculated the ratio R4/16l. The value of this ratio varied (p=0.016), and the ROC analysis showed high sensitivity and specificity of the criterion. This makes it possible to use this ratio as a diagnostic criterion for partial nasolacrimal duct obstruction.
