Detection of Cytokines in Tears

The tear film provides a refractive optical surface of the eye and nutrients to the underlying epithelial cells; it also contains factors that protect the eye from invasion by foreign particles including microorganisms. The tear film can alter rapidly from a basal state that occurs during the daytime, to the extremes of a rapidly increased lacrimation that occurs during crying (either as the result of physical trauma or emotional trauma) or a cessation of tear flow that occurs during eye closure. During these changes the protein and lipid components of the tear film have been shown to alter dramatically. Antibacterial proteins such as lysozyme and lactoferrin are designated as regulated protein, i.e., their concentration as a function of tear volume does not alter during increased lacrimation (1 ). On the other hand, secretory IgA, the predominant immunoglobulin in tears, is a constitutively secreted protein, i.e., its concentration alters during changes in lacrimation (1 ).