An improved method for measuring human tear lysozyme concentration
P. Velos, P. M. Cherry and D. Miller
Previously described methods for measuring human tear lysozyme are fraught
with shortcomings. A new method has been devised. Tear fluid was collected
on Whatman filter paper discs. Each disc was placed in a tightly capped
tube containing sodium phosphate buffer. Fluid from each tube was placed
directly into a well of the lysozyme immunodiffusion plate. After the
precipitation rings had reached maximum size, their diameters were
measured. A linear standard curve was constructed, and lysozyme
concentration was expressed as micrograms per milliliter. The tear lysozyme
concentration was obtained from the standard curve and corrected for the
assay dilution factor. The mean tear lysozyme concentration in 15 normal
patients was 1.4 +/- 0.5 mg/mL. In ten patients with dry eyes, the mean was
0.7 +/- 0.5 mg/mL. The method used to collect, store, and transport tears
is easily performed in the clinic and readily tolerated by patients. The
technique of radial immunodiffusion is reliable and simple, compared with
other assays.
