Effect of Age on Human Tear Film Evaporation in Normals

Abstract

The evaporation of fluid from the tear film accounts for between 10 and 40% of the elimination of tears from the human eye^1.2. Attempts have been made to measure the rate of evaporation using different techniques. More than 30 years ago Mishima and Maurice³ used assessments of tear film thickness as an indicator of the rate of fluid loss. A vapor pressure gradient technique was originally used by Hamano et al⁴ and later modified to be Jess invasive by Tomlinson and Trees⁵. Different methods for measuring the relative humidity within a goggle-cup over the eye have been employed by Tomlinson and Cedarstaff⁶, Rolando and Refojo⁷ and Tsubota and Yamada⁸. The differences in technique account for some of the variability observed in the determination of human tear film evaporation, values between 4.07 and 67.1 having been recorded for normals.^4,5,7,8