Although various sampling methods of tears from conjunctival sac have been reported, no previous study compared their effectiveness or efficiency based on protein extraction. By comparing the compliance, volume and protein concentration of each tear sampling method, we searched for the most efficient tear collection method.

Resting tear samples of 14 eyes of normal subjects were collected using Schirmer paper, capillary tube, cellolose acetate rod and 3 different ophthalmic sponges made of different materials and density (Merocel®, KeraCel® and Weck-Cel®). After centrifugation of the collected tear samples, the tear volume and protein concentration were measured for each method. Additionally, the compliance of each tear sampling method was analyzed by numerically representing the amount of discomfort experienced during resting tear collection.

The average volume retrieved by each tear sampling method was 9.0 ± 1.1 µL with no significant differences between groups. The average concentration of protein retrieved by each tear sampling method was 5.3 ± 1.2 µg/µL. Merocel® retrieved 7.6 ± 0.61 µg/µL, which was significantly higher than other sampling methods ( p < 0.05). The compliance of Merocel® and the capillary tube were the highest, while KeraCel® showed the lowest compliance.

Merocel® retrieved the highest amount of protein and showed high compliance and may be the most effective and easily applicable tear sampling method in clinical settings.