Characteristics of the pre-lens tear film during hydrogel contact lens wear

The integrity of the pre-lens tear film (PLTF) is an important determinant of the clinical performance of contact lenses. The PLTF of eight hydrogel lenses, ranging from 36.5% to 85% water content, was assessed on six asymptomatic lens wearers in a randomized, double-masked experiment. Using a specular reflection technique, the thicknesses of the lipid and aqueous phases were found to be greater on lenses of higher water content. Water content was measured before and after 90 min wear using a hand-held refractometer. Non-invasive tear break-up time was also found to be greater for higher water content lenses. No association was found between lens dehydration and PLTF characteristics. The differences in PLTF noted in this study may help to explain the differences noted between some lenses in their rates of surface deposition