Air pollutants and tear film stability - a method for experimental evaluation

Instability of the pre-ocular tear film causes symptoms of dry eyes. Tear f ilm instability may be caused by exposure to air pollutants, but identifica tion of causative agents is often difficult. We describe an in vitro techni que for assessment of putative agents on the surface activity of Meibomian lipids. The lipids were obtained from bovine eyelids and dissolved in chlor oform. Surface activity of the solution was assessed on a Wilhelmy balance. After addition of benzalkonium chloride, minimum surface tension of the li pids increased and maximum surface tension fell. After addition of quartz p articles, both maximum and minimum surface tension increased. The method ca n be used to screen substances suspected to cause dry eyes, providing a bas is for selection of substances for in vivo studies.