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Elisabeth M Messmer, Markus M. Schaumberger, Siegfried Priglinger, Susanna F. Koenig; Evaluation of tear film osmolarity using Tearlab® and I-Pen® osmometry. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6773.
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© ARVO (1962-2015); The Authors (2016-present)
To compare tear film osmolarities in normal individuals as measured by Tearlab® and I-Pen® osmometers.
51 healthy subjects (mean age 40.6 years, range 17-63 years, 66.7% females) without dry eye disease (Ocular surface disease index < 13, tear film break up time > 7 seconds, normal Schirmer-test > 10 mm/5 minutes) were included in this study. Tear film osmolarity was measured in the tear meniscus (Tearlab®) and in the palpebral conjunctiva (I-Pen®) with a 30-minute interval. Statistical analysis was performed using Wilcoxon tests and Spearman correlations.
Mean Tearlab® osmolarities were 295.1 mOsm/l (right eye), 294.0 mOsm/l (left eye), and 294.6 mOsm/l (mean of both eyes) with a range of 268 to 394 mOsm/l. I-Pen® measured mean osmolarites of 301.6 mOsm/l (right eye), 302.5 mOsm/l (left eye), and 302.1 mOsm/l (mean of both eyes) with a range of 268 to 394 mOsm/l. There was a significant difference in tear film osmolarities for the two techniques for both single eyes (p<0.02) and the mean value of both eyes (p<0.001). Tearlab® and I-Pen® measurements did not correlate significantly in any eye (r=0.27 and r=0.08 for right and left eye, accordingly). When considering a cut-off value of 308 mOsm/l (as suggested for Tearlab®), 98.0% of Tearlab® values and 68.6% of I-Pen® values were located in the normal range.
I-Pen® measured significantly higher tear film osmolarities than Tearlab®. The location of the measurement site in the palpebral conjunctiva could be responsible for this difference. Our preliminary results indicate that higher cut-off values between 316 and 320 mOsm/l should be considered when using I-Pen® for evaluation of tear film osmolarity.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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