A spectrophotometric method for quantitative determination of lysozyme in human tears: description and evaluation of the method and screening of 60 healthy subjects.
A spectrophotometric micromethod for lysozyme determination in tears is described, which enables the estimation of very low concentrations of lysozyme in individual tear samples, and which can be performed rapidly. The method is based on collecting the tears by a microcapillary tube and diluting them in a special manner which increases the volume of the tear sample, thus making possible analysis of other tear constituents in addition to lysozyme. Lysozyme activity in tears is determined by reduction of optical density (OD) of Micrococcus lysodeikticus suspension. The sensitivity of the method was determined on the basis of repetitive readings. The level of lysozyme in tears of 60 healthy people was determined by this method and found to be 6.1 mg. per milliliter hen egg lysozyme (HEL) with standard deviation of 1.57 mg. per milliliter HEL or 1.5 mg. per milliliter human tear lysozyme (HTL) with standard deviation of 0.39 HTL. Lysozyme level in tears of both eyes of each individual is equal, and any difference observed between the two eyes is due to the variability of the method.