Viscosity-dependent fluid dynamics of eyedrops on the ocular surface

PURPOSE: To determine whether the viscosity of eyedrops affects the distribution of the precorneal tear film. METHODS: Using a differential pachymetry map, we obtained tear film thickness in healthy volunteers before and after the instillation of nonviscous, aqueous artificial tears and a 0.3% sodium hyaluronate solution. RESULTS: The instillation of aqueous artificial tears disclosed a significant (P < .05) thickening of the superior cornea] tear film compared with the inferior corneal tear film. The increase in thickness by 0.3% sodium hyaluronate solution was uniform, with no differences between the superior and inferior cornea. CONCLUSIONS: Aqueous artificial tears caused an uneven thickening of the precorneal tear film, with most of the thickening observed at the superior cornea. Lower sections of the cornea may benefit less from the instillation of nonviscous solutions.