Artificial Tear Drops Influence on High Order Aberrations in Healthy Eye Subjects

Purpose: To gain more insight into tear film from a functional standpoint, we investigate artificial tear eye drops effect by assessing its influence on high order aberration in healthy eye subjects using a Shack-Hartmann aberrometer. Methods: An observational case-control study into which 20 young healthy participants were involved. High order aberrations were measured using Shack-Hartmann technology before; 1 hour and 3 hours after instillation of a 0.3% sodium hyaluronate eye drop. Main measured outcomes were root mean square of high order aberrations in central 5 mm (HOA 5) and in central 6 mm (HOA 6), spherical aberration, vertical coma, horizontal coma, vertical trefoil, horizontal trefoil. Results: The HOA 5 mean value was 0.21µ before the instillation of artificial tear eye drops and 0.185µ one hour after instillation with a significant statistical difference (p=0.01) and 0.186µ three hours after instillation with no significant statistical difference (p=0.057). No significant statistical difference was found for HOA 6 before and after tear eye drops application. Vertical coma was the only subset of high order aberrations that was significantly improved from 0.042µ to -0.003µ one hour after tear eye drops application (p=0.04). There was no statistical difference for all the other measurements. Conclusions: Some high order aberrations could arise from the tear film even in a healthy patient. Vertical coma could be used as a tool to point to the integrity of tear film. For wavefront-guided refractive surgery candidates, high order aberrations should be assessed 1 hour after artificial tear drop instillation.