(11a) Viscoelasticity of Meibomian Lipids and Their Role on the Development of Evaporative Dry Eye

Dry eye disease (DED) is a group of pathologies leading to ocular surface damage. Among other burdens, DED increases healthcare costs, and reduces of the quality of life of sufferers.

DED occurs when the fluid covering the surface of the eye, or tear film, loses its homeostasis. Specifically, in evaporative dry eye, the evaporation of the tear film is higher than the natural renewal of tears. One of the means the eye regulates the evaporation is through the Tear Film Lipid Layer (TFLL), a 50-200 nm layer of a mixture of lipids on top of the Tear Film. It is composed by approximately 60-70% nonpolar lipids (wax esters, cholesterol and cholesterol esters), and 15% of polar lipids (phospholipids and glycolipids). The principal source for those lipids are the Meibomian glands, located inside the lids. To accomplish the retardation of evaporation, the TFLL must form a stable, continuous film that resist the compression and expansion cycles due to blinking.

In previous studies, we have found a significant increase of the evaporation rate patients suffering Meibomian diseases, compared vs. healthy controls. In this work, we measured the bulk rheology of Meibomian lipids cases and controls, using a Quartz Microbalance with Dissipation, as well as the surface rheology of Meibomian lipid layers by the method of oscillation of a pending drop. This study may help in the development of novel therapeutics for the treatment of dry eye syndrome.