Investigation of the repeatability of tear osmolarity using an I-PEN osmolarity device.

Purpose: To investigate the repeatability of tear osmolarity in healthy Saudi subjects using an I-PEN osmolarity device.

Materials And Methods: Thirty typical male subjects with healthy eyes (27.4 ± 4.9 years) participated in the study. Eye abnormalities were tested with a slit lamp, and eye comfort was determined with the surface disease index. Measurements of the tear break-up time and phenol red thread tests were used for as exclusion criteria. The tear osmolarity test, using an I-PEN osmolarity system, was performed three times in the right eye of each subject with a 5 min' gap between tests.

Results: The average osmolarity test score was 303.8 ± 4.8 mOsm/L. Tear osmolarity measurements showed tear osmolarity of 280-299 mOsm/L, 300-309 mOsm/L, and 310-329 mOsm/L in 14 (46.7%), three (10%), and 13 (43.3%) subjects, respectively. Correlations among the three I-PEN measurements were significant (Spearman's correlation coefficient; = 0.036, 0.501, and 0.603; = 0.050, 0.006, and 0.001, respectively). The mean coefficient of variance among the three measurements was 4.4%.

Conclusion: The mean measurement of an I-PEN tear osmolarity was 303.8 ± 4.8 mOsm/L which is in agreement with the range of those reported for healthy subjects. The I-PEN is reliable and has the advantage of portability (hand-held) compared to the other osmolarity systems.