The effect of collection technique on tear composition.

Selected proteins were quantitated after collecting samples of the tears by using two sampling techniques. Tears from the same individual were collected via absorption by Schirmer filter paper strip from the unanesthetized, inferior, conjunctival sac and were compared with tears collected by a capillary tube (taking care not to touch the conjunctiva), after stimulation of tearing by irritation of the nasal mucosa with ammonia vapor. Tear samples were quantitated immunochemically for two typical lacrimal proteins, lysozyme and lactoferrin, and three typical serum proteins, albumin, transferrin, and IgG. Tear analysis of all constituents were performed on a single sample of tears collected by each method from the same individual. Normal subjects without ocular pain or discomfort comprised a sample of 12 subjects ranging in age from 19 to 57 years and consisting of 9 men and 3 women. Concentrations of lysozyme and lactoferrin in samples collected by either method were not significantly different. In contrast, the concentration of albumin, IgG and transferrin collected by Schirmer filter paper technique was significantly higher (P less than 0.01) than the concentration in tears collected by the capillary tube technique. A highly significant increase in serum proteins was seen when the Schirmer filter paper strip was used to collect tears compared to tears collected without mechanical stimulation of the conjunctiva.