***Looking for participants in research study on tear film thickness*** Earn $20/hr for helping us to research tear film thickness and dynamics. We will acquire short videos of your eye that allow us to determine the film thickness from colorful interference patterns. Sessions will last approximately an hour, and you may participate in more than one session. For more information please contact Sophie Lohmann at lohmanns@stanford.edu or Dr Juho Pokki at jpokki@stanford.edu