Lipid Gradient in Tear Film (IMAGE) Hokkaido University Caption The team suggests that OAHFA, OAHFA derivatives and other lipids together form a polarity gradient which plays an important role in connecting the lipid layer and liquid layer of the tear film. Credit Hokkaido University Usage Restrictions This illustration is copyrighted and can be used for reporting this research work without obtaining a permission by crediting it as instructed. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.