Characterization of tear dynamics

Abstract

AbstractPurpose: Tear film is important in eye optics due to its influence on dry eye, contact lenses fit, etc. After blinking, it starts to evaporate causing the film to thin. While thinning in the eye center, the tear maintains a constant thickness around the eyelids (meniscus), which is easy to measure. This work aims to study tear film dynamics based on the meniscus and dry eye‐related parameters.Methods: A hybrid OCT‐iVue was used to measure the lower meniscus for several subjects. The dynamics of the tear were simulated with a precorneal tear film model after blinking [1], introducing the tear geometric parameters as well as physical parameters (viscosity, evaporation, surface tension, etc). The model uses the standard parameters given in [1], changing the values of the meniscus, viscosity, and surface tension to test different patients and dry eye conditions.Results: The tear film thickness was calculated for patients with the different meniscus. The model shows a tear thinning over time (additional drop before each meniscus). In the central eye, there are slight oscillations that are more pronounced for higher meniscus, increasing pressure. The greater meniscus seems to have greater spatial stability. The method allows the study of the spatial–temporal oscillations of tears and relates them to their physical parameters.Conclusions: Tear stability appears to be related to the ocular meniscus and greater stability is observed for the larger meniscus. Dry eye characteristics appear with high viscosity and medium surface tension. Additional mathematical studies should be done to clarify the influence of different tear parameters and their measure in different patients.Reference1. Braun R.J., et al. Modelling drainage of the precorneal tear film after a blink. Math Med Biol 2003; 20: 1–28.