Purpose: To characterize a method of tear collection based on the use of amphiphilic polyurethane absorbing minisponges.
Methods: Tear fluid was collected from 17 healthy volunteers. A preweighed polyurethane dry minisponge was laid on the margin of the lower eyelid. Once wet (5-10 minutes), the fluid was transferred to a preweighed Eppendorf tube after squeezing the sponge by centrifugation. The amount of fluid absorbed and fluid recovered were determined by reweighing the sponge and the tube after absorption and centrifugation steps, respectively. The fluid was qualitatively characterized by electrophoretic polypeptide profiling in Coomassie blue-stained SDS-polyacrylamide gels.
Results: Per eye, 14.6 ± 5.3 μL tear fluid was collected. That volume was about 90% of the fluid absorbed by polyurethane minisponges, almost doubling the fraction recovered from other more hydrophilic absorbing polymers. Major bands characterizing the electrophoretic profile of this fluid were those of 79, 66, 27, 18, and 14 kd. This profile was indistinguishable from that of tear fluid aspirated into glass microcapillaries. Tear fluid collected simultaneously from both eyes displayed the same profiles. Successive tear samples from a single eye showed the same profile except for the 66-kd band, which increased steadily as collection proceeded. Tear donors rarely complained of discomfort.
Conclusions: Tear collection by absorbing polyurethane minisponges is highly advantageous in efficiency (recovery) and reproducibility (invariant electrophoretic polypeptide profiles). Tear donor comfort, simultaneous bilateral collection, and collections from several donors at once are additional major advantages of this collection method in studies involving single subjects and populations in health and disease.