Interface Properties of Simplified Tear-Like Fluids in Relation to Lipid and Aqueous Layers Composition

Abstract

The natural tear fluid forms a thin covering over the surface of the cornea and conjunctiva and serves a number of vital functions.ⁱ It produces an optically smooth surface, provides a barrier to microorganism and particulate debris, delivers nutrients to the underlying tissue, and lubricates the movements of the eyelid. It is a dynamic structure with continual turnover of its constituents, and the layer is regenerated after each blink. Failure of the tear film leads to a number of clinical pathological conditions known collectively as Dry Eye Syndrome. The structure and composition of the tear film have been described in some detail,^ii,iii and its importance greatly debated because of its relevance for the experimental and therapeutic management of dry eye. However, physiological function is dependent on the physical properties of the components, an understanding of which is emerging more slowly. Consequently, the development of therapeutic stratagems for Dry Eye Syndrome and, in particular, of synthetic tear substitutes remains quite pragmatic.