Cytokines and tear function in ocular surface disease.

In summary, tear EGF levels correlate most strongly with tear production in normals, and it is likely that some form of homeostatic mechanism exists to provide a constant supply to the ocular surface. Commercial ELISA kits appear to measure EGF in tears with good consistency and may be useful in the future to improve comparability of data from different studies. In addition, in ocular rosacea, which mimics keratoconjunctivitis sicca in a number of respects, there is a differential increase in the level of the inflammatory cytokine IL-1 alpha in the tear fluid. Much of this elevation appears to be the result of reduced tear turnover, which may form an important positive feedback mechanism encouraging tear stagnation and the perpetuation of ocular surface inflammation.