Tear film stability: a review.

Tear film stability can be assessed via a number of tools designed for clinical as well as research purposes. These techniques can give us insights into the tear film, and allow assessment of conditions that can lead to dry eye symptoms, and in severe cases, to significant ocular surface damage and deterioration of vision. Understanding what drives tear film instability and its assessment is also crucial for evaluating existing and new therapies.

Interfacial dilatational viscoelasticity of human meibomian lipid films.

Purpose/aim: The meibomian lipid layer is able to withstand the enormous stresses and deformations that occur during blinking due to the combination of its elastic and viscous properties. The purpose of this study was to measure the dilatational viscoelasticity of in vitro meibomian lipid films and compare how these properties differ between room temperature and physiological temperatures. Viscoelasticity was also compared with meibomian lipid films seeded with cholesterol or β-carotene (the levels of these lipid species change in disease states).

The interfacial viscoelastic properties and structures of human and animal Meibomian lipids.

As the interface between the aqueous layer of the tear film and air, the lipid layer plays a large role in maintaining tear film stability. Meibomian lipids are the primary component of the lipid layer; therefore the physical properties of these materials may be particularly crucial to the functionality of the tear film. Surface pressure versus area isotherms, interfacial shear and extensional rheology, and Brewster angle microscopy (BAM) were used to characterize the Meibomian lipids from different species known to have different lipid compositions.