The role of meibomian secretion in the tears.

Meibomian lipid promotes the formation and stabilisation of the precorneal tear film. The deposited layer of this material at the lid margins prevents entry into the eye of skin surface fatty acids which would disrupt the film. The external oily layer also acts to reduce the rate of evaporative loss of fluid from the tear film. The relationship between composition of the secretion and its physical properties is discussed.