Human tear lysozyme. A comparison of electro-immunodiffusion, radial immunodiffusion and a spectrophotometric assay.

In 116 persons (67 men and 49 woman) the tear fluid of both eyes was collected using paper discs and once more after topical anaesthesia. After weighing the discs and eluting the tear fluid, the lysozyme content was measured using two immunological methods [radial immunodiffusion (RID) and rocket immuno-electrophoresis (RIE)] and a spectrophotometric assay. Standard curves were established with purified human lysozyme and egg-white lysozyme. In addition, albumin was determined in all the samples by rocket immuno-electrophoresis. All lysozyme assays showed a high degree of correlation, the spectrophotometric technique giving significantly lower values (compared with RID and RIE) when human lysozyme was used for standardization. The lysozyme content of the tears did not correlate with the fluid uptake in the discs, but showed a significant decrease with age, which was abolished by topical anaesthesia. In contrast, albumin levels were dependent upon the weight and independent of the age of the patient. It is suggested that the determination of albumin as a "reference protein' might help in comparing the results of different tear sampling techniques used by various groups, which induce variable amounts of reflex tearing.