Dynamic viscosity of the wall of the lacrimal sac in disorders of the patency of the lacrimal ducts.

PURPOSE: To assess the dynamic viscosity of the lacrimal sac wall in patients with various origins of lacrimal duct obstruction.

METHODS: The study was performed in 35 cases: 21 cases with primary nasolacrimal duct obstruction (PANDO) and 14 cases with secondary nasolacrimal duct obstruction after radioiodine therapy (SALDO). The study of biomechanical properties of the lacrimal sac was carried out using a test bench. The principle of the study was to indent the sample at a given speed and record the data obtained from the sensor of the force transmitted to the sample. The area under the curve (AUC) and the peak viscosity were calculated. A qualitative characteristic of the obtained curve was given.

RESULTS: Median AUC in patients with PANDO was 17 × 106 [6 × 106 ; 19 × 106 ] N/m2  × s, in patients with SALDO 21 × 106 [13 × 106 ; 25 × 106 ] N/m2  × s. Intergroup differences were statistically significant (p = 0,048). The median peak viscosity in PANDO patients was 29 × 106 [25 × 106 ; 35 × 106 ] N/m2 , in patients with SALDO 32 × 106 [21 × 106 ; 41 × 106 ] N/m2 . The qualitative characteristics of the obtained curves differed.

CONCLUSION: Biomechanical properties of the lacrimal sac may vary depending on the cause of obliteration of the lacrimal ducts. The integrated dynamic viscosity is significantly higher in SALDO patients due to exposure to radioiodine compared to that in PANDO patients.