(319g) Quantifying Effects of Polar Lipid Proportions on Model Tear Film Stability

The human eye is covered by a thin liquid film called the tear film which protects the ocular surface and aids in vision. Although a healthy and stable tear film is needed to prevent a number of widespread ocular surface diseases, including dry eye syndrome (DES), the tear film components responsible for preventing premature destabilization of the tear film remain unclear. While a growing body of work has been dedicated to characterizing the effects of compositional changes in the outermost lipid layer of the tear film, little work has been done to link these changes to quantitative measures of tear film stability.

One commonly accepted model of the tear film splits the lipid layer into two subphases - a nonpolar lipid phase, which contacts air, and a polar lipid phase, which resides at the interface between the aqueous layer and the lipid layer. Phospholipids are generally assumed to be the main constituent of the polar lipid phase and are believed to play an important role in stabilizing the tear film, in part due to their ability to reduce the critical film thickness for dewetting of thin films.

However, despite recent efforts to investigate the role of phospholipids in tear film stability, the effect of changes in the lipid layer’s phospholipid proportion on tear film stability is still not fully understood. To address this gap, we will investigate how varying proportions of the phospholipid dipalmitoyl phosphatidylcholine (DPPC) in the lipid layer affect the stability of a simplified in vitro model tear film comprised of artificial tear solution (ATS), DPPC, and stearyl stearate, which model the aqueous layer, polar phase of the lipid layer, and nonpolar phase of the lipid layer, respectively.

We will first quantify tear film stability through use of the previously developed Interfacial Dewetting and Drainage Optical Platform (i-DDrOP), which allows for the spatiotemporal imaging of thin liquid films over curved substrates. We will then characterize the surface properties of these model tear films with measurements of surface tension and interfacial viscoelasticity to investigate how surface rheology impacts tear film stability in this system. Altogether, this work aims to advance our understanding of the role of phospholipids in stabilizing human tear films, in an effort to illuminate fundamental causes of ocular surface diseases such as DES and guide future avenues of therapeutic research.