Effect of preservatives in artificial tear solutions on tear film evaporation

It has been suggested that certain preservatives in artificial tears may affect the stability of the tear film lipid layer. In the present study, tear film evaporation rate (TER) was measured with a modified Servomed Evaporimeter to determine whether preservatives affected tear stability. Two solution combinations were compared in a cross-over study of eight non-contact lens wearers. These combinations consisted of identical solutions, one preserved with either benzalkonium chloride (0.004%) or chlorobutanol (0.5%), the other non-preserved. Grouped data analysis showed no significant difference in TER with either solution combination. Individuals showed differences, but these were not related to the preservative. It is suggested that these concentrations of chlorbutanol and benzalkonium chloride did not affect the stability of the tear film lipid layer as indicated by an altered TER.