Currently, most contact lenses are made with a silicone hydrogel (Si-Hy) blend that provides softness for comfort as well as high oxygen permeability. Silicone hydrogel lenses have both hydrophilic and hydrophobic areas, and the natural hydrophobicity of the material contributes to biofouling, which is the adsorption of proteins and lipids from the tear film of the eye. Published in vitro investigations into the quantity and spatial distribution of lipids deposited on contact lenses usually involve the use of artificial tear fluid (ATF) that is not changed or replenished over the course of the experiments. Yet, the natural tear film is constantly replenished by the meibomian and lacrimal glands. The intent of this study was to investigate the significance of replenishing the ATF over the study period on lipid absorption profiles and quantities. In part one, fluorescence confocal microscopy was used to observe the penetration profiles of lipids into nine different Si-Hy lenses. In part two, radiolabeling was used to quantify the amount of lipid absorbed by nine different Si-Hy lenses. Using a non-static exposure method was found to allow more absorption of cholesterol than the static method. The non-static method also provided more differentiation between lens types and brands in lipid absorption profiles and amounts than the static method.
