Reproducibility and repeatability of the OcuSense TearLab™ osmometer

Some studies report that increased tear osmolarity is a reliable indicator of dry eye syndrome (DES). The OcuSense TearLab (TM) osmometer requires less than a 100-nl sample of tears and provides an instant quantitative result. Our aim was to clinically evaluate this instrument in terms of its reproducibility and repeatability. Twenty-nine participants who ranged in age from 19 to 49 years (mean +/- SD: 23.3 +/- 5.5 years) were recruited. Osmolarity readings were collected by two operators, in two sessions separated by 1 or 2 weeks in order to assess test reproducibility and repeatability. The coefficient of reproducibility was 39 mOsms/l; the coefficient of repeatability was 33 mOsms/l. Our mean coefficient of variation over four readings for 29 subjects is 2.9%, which compares well with that reported by the manufacturer. Our results inform practitioners about the level of change over time that can be considered clinically relevant for healthy subjects. This value is 33mOsms/l; any change smaller than this could be attributed to measurement noise.