Influence of Interfacial Rheology on Stabilization of the Tear Film

The tear film covers the surface of the eye, protecting and lubricating the cornea. Of particular interest in this presentation is meibum, a viscoelastic insoluble lipid layer that is spread from the glands lining our eyelids. Past work has focussed on the role of this oily layer in reducing evaporation, although conflicting evidence on its ability to reduce evaporative loss has been published. We present here the beneficial effects that are derived through the interfacial viscoelasticity of this meibum layer.

Using interfacial rheology measurements, meibum is shown to be remarkably viscoelastic. By measuring the drainage and dewetting dynamics of thin aqueous films capped with viscoelastic insoluble layers, we offer evidence that these layers strongly stabilize the films because of their ability to support surface shearing stresses. Our findings suggest an alternative view for the role played by meibum in the tear film. This view can help explain the origin of meibomian gland dysfunction, or dry eye disease, where abnormal compositions of the lipid mixture fail to offer the proper mechanical resistance against rupture and dewetting of the tear film.