The human lacrimal apparatus produces and maintains the tear film over the eye's exposed anterior surface. This film is a complex biological mixture containing enzymes, glycoproteins, immunoglobulins, and several undefined proteins. Two incompletely characterized proteins are a soluble sialyglycoprotein that increases in the closed eye tear fluid and a protein that keeps the ocular surface free of deposits. Isolating and characterizing these proteins, accompanied by identifying the tissues of origins and signals responsible for their release, would be extremely useful to understand the dynamics of the external ocular environment.

Previously, we improved the protein-blocking assay for the surface active protein and identified HPLC fractions that contain the surface active tear substances. This activity is greater than that produced by known commercially available surfactants. We compared activity from tear samples obtained under different conditions and found that the surface active material seems to be secreted from the lacrimal gland.

Also, we separated the sialylglycoprotein from tear fluid, especially from the closed eye, and localized the sialylglycoprotein to the ocular surface epithelium by extraction techniques and immunofluorescence microscopy. Currently, we are exploring an antiprotease activity of the sialylglycoprotein.

We are concentrating on the isolation and characterization of the proteins in the tear film with the longterm goal of determining whether changes occur in the concentration of one or both of these proteins in individuals who have keratoconjunctivitis sicca (dry eye syndrome) or other pathologies of the external eye. This information may be useful in diagnosing keratoconjunctivitis sicca and/or developing a biologically designed wetting solution.