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Gerhard Garhofer, Semira Kaya, Johannes Nepp, Doreen Schmidl, Leopold Schmetterer; Reproducibility of tearfilm osmolarity measurement assessed with electrical impedance in patients with dry eye syndrome and healthy subjects. Invest. Ophthalmol. Vis. Sci. 2013;54(15):937. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Dry Eye Syndrome (DES) is a common medial condition that affects up to 20% of adults aged 45 years or older. Standard clinical tests are limited by their poor reproducibility and show only a weak correlation to patients complains. It has been hypothesized that measurement of tear film osmolarity may be a new and promising non-invasive approach for the diagnosis and monitoring of treatment success. The current study investigated the short time and day-to-day reproducibility of the Tear Lab Osmolarity system.
20 patients with DES and 20 age and sex matched volunteers were included in this study. Tear film osmolarity was measured in both groups on three consecutive study days to calculate day-to-day reproducibility. To assess short time reproducibility of osmolarity measurements were taken 3 times per study day. Tear film break up time (BUT) and Schirmer 1 test were assessed by standard clinical tests. Coefficient of variation was calculated as a measure of reproducibility.
Schirmer test and BUT was lower in patients with DES compared to healthy subjects on all three study days (p<0.05).Tear film osmolarity was significantly higher in patients with dry eye compared to healthy controls on day 1.(DES:311±11 mOsml/l; healthy: 301±12 mOsml/l, p=0.02 between groups) This was also true for day 2 (DES:309±11 mOsm/l; healthy:299±11mOsml/l, p=0.01 between groups) and day 3 (DES:308±12 mOsml/l; healthy: 298±11mOsml/l, p=0.01 between groups). The overlap between the groups was, however, high. Calculated test-retest coefficient of variation (cv) in tearfilm osmolarity on each day was 3.18%±2.89%, 2.81%±2.08% and 2.23%±1.85%, respectively. Day-to-day variability as calculated by the cv between the three study days was 3.47%±1.69%.
Our results indicate good short-time and day-to-day reproducibility of the osmolarity measurements. Large scale longitudinal clinical studies are needed to investigate whether tear film osmolarity is a suitable surrogate parameter for diagnosis of DES and monitoring disease progress.
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