Protecting Tear-Film Stability under Adverse Environmental Conditions Using a Mucomimetic with a Non-Newtonian...

Background and Objectives: Tamarind-seed polysaccharide (TSP) and hyaluronic acid (HA) have mucoadhesive properties that improve drug absorption and delay in drug elimination from the ocular surface. We aimed to evaluate TSP/HA-containing formulation for its efficiency in dry-eye symptoms induced by adverse environments and the interaction between mucomimic polymer and tear-film parameters. Materials and Methods: The participants were exposed to 5% relative humidity (RH) in a Controlled Environment Chamber (CEC) under constant room temperature (21 °C). Tear-film parameters were assessed at 40% RH and 5% RH. Rohto Dry Eye Relief drops were used in the two treatment modalities, protection (drops instilled before exposure to the dry environment) and relief (drops instilled after exposure to the dry environment). The HIRCAL grid, Servomed EP3 Evaporimeter, and Keeler's TearScope-Plus were used to screen for non-invasive tear break-up time (NITBUT), tear evaporation rate, and lipid-layer thickness (LLT) using protection and relief treatment methodology. Results: LLT was found to be significantly thinner at 5% RH compared with at 40% RH (p = 0.007). The median LLT dropped from 50-70 nm (grade 3) at 40% RH to 10-50 nm (grade 2) at 5% RH. TSP/HA eye drops significantly augment LLT in both treatment modalities, protection (p = 0.01) and relief (p = 0.004) at 5% RH. The mean evaporation rate doubled from 40.93 at 40% RH to 82.42 g/m²/h after exposure to 5% RH. In protection mode, the TSP/HA allowed the average evaporation rate to be much lower than when no TSP/HA was used at 5% RH (p < 0.008). No alteration in evaporation rate was recorded when the TSP/HA drop was used after exposure (relief). The mean NITBUT was reduced from 13 s in normal conditions to 6 s in the dry environment. Instillation of TSP/HA eye drops resulted in significant improvement (p = 0.006) in tear stability, where the NITBUT increased to 8 s in both protection (before exposure) and relief (after exposure) (p = 0.001). Although improved, these values were still significantly lower than NITBUT observed at 40% RH. Conclusions: Significant protection of tear-film parameters was recorded post instillation of TSP/HA eye drop under a desiccating environment. Both treatment methods (protection and relief) were shown to be effective. The presence of TSP/HA enhances the effectiveness of teardrops in protecting the tear-film parameters when exposed to adverse environments.