The Effect of Meibomian Lipids and Tear Proteins on Evaporation Rate under ControlledIn VitroConditions

Abstract

The lipid layer of the tear film is associated with preventing evaporative loss. The ability of human Meibomian lipids to reduce evaporation in vitro was tested. Films of human or animal Meibomian lipids or mixtures of cholesterol and phosphatidylcholine were spread on the surface of either artificial buffer or on whole tears and placed on a mass balance that was enclosed in a sealed chamber. The temperature was adjusted to 37 degrees C and gas flow was controlled. Increasing the amounts of Meibomian lipids gave a very small reduction in evaporation. It was concluded from these in vitro experiments that prevention of evaporation from the tear film is not due to the Meibomian lipids alone, but is more likely to be due to a complex interaction between components of the aqueous and the Meibomian lipids.

The real reason for having a meibomian lipid layer covering the outer surface of the tear film – A review

“…By contrast, Brown and Dervichian (1969) were unable to show that a spread film of human meibomian lipids at 37 C prevented evaporation. Herok et al (2009) also found that in vitro a meibomian lipid layer did not prevent evaporation. This contrasted with an earlier publication from the same group where it was shown that bovine meibomian lipids reduced evaporation from a pendant drop (Miano et al, 2004).…”

Four Characteristics and a Model of an Effective Tear Film Lipid Layer (TFLL)

“…56,57 Similarly, artificial TFLL compositions have little or no effect on evaporation. 58,59 Herok et al therefore proposed that prevention of evaporation by the TFLL requires a complex interaction between components of aqueous tears and meibum.…”

“…58,59 Herok et al therefore proposed that prevention of evaporation by the TFLL requires a complex interaction between components of aqueous tears and meibum. 57 The in vitro evaporation resistance of meibum may also be readily disturbed by experimental procedures. In this respect, it may be noted that high evaporation resistance is difficult to achieve even in laboratory conditions.…”

Lacritin Rescues Stressed Epithelia via Rapid Forkhead Box O3 (FOXO3)-associated Autophagy That Restores Metabolism

“…Stress is sudden and varied on surface epithelia, particularly on the eye where the cornified barrier protecting skin is replaced by tears, the ϳ3-m-thick fluid comprising metabolites (9), lipids (10), and in a recent estimate over 1500 different proteins (11). Homeostatic dysregulation of the surface of the eye in "dry eye," a tear insufficiency syndrome(s) and the most common eye disease (12), offers some potential etiological clues because surprisingly few tear proteins show any disease-associated change.…”