Quantitative tear lysozyme assay in units of activity per microlitre.

An accurate method of assaying the tear lysozyme concentration in units of activity/mul has been developed. Normal physiological levels which vary with age have been determined. It has been demonstrated that measurement of the volume of tear fluid collected and assay with a calibrated standard are essential for the accurate determination of the precise concentration of lysozyme in the tear fluid. Tear lyozyme concentration can be used as an index of lacrimal gland function, and in the diagnosis of the sicca syndrome and associated conditions. We believe that this method of tear lyozyme assay has important applications in drug toxicity states in humans (for example, practolol toxicity) and also in animal drug toxicity studies.