The TearLab Osmolarity Test Card, in conjunction with the TearLab Osmolarity System, provides a quick and simple method for determining tear osmolarity using nanoliter (nL) volumes of tear fluid collected directly from the eyelid margin. The Test Card is held by the Osmolarity Test Pen, for safe collection.
The TearLab Osmolarity Test utilizes a temperature-corrected impedance measurement to provide an indirect assessment of osmolarity. After applying a lot-specific calibration curve, osmolarity is calculated and displayed as a quantitative numerical value.
To learn how to perform the test, see our Training Videos.
The MAXIMUM of the eyes
Measurements >300 mOsm/L demonstrate loss of homeostasis. Diagnosis and treatment decisions should be guided by the higher measurement.1
The DIFFERENCE of the eyes
Tear Film Instability
A difference between eyes 8 mOsm/L or greater (intereye difference) indicates instability of the tear film and is a hallmark of dry eye disease.1
The Coefficient of Variation of the TearLab Osmolarity System
is lower (better) than most point-of-care lab tests and comparable to the most sophisticated laboratory technologies.
Lab Test: Osmolarity
Lab Test: Glucose
Lab Test: Cholesterol
References: 2, 3, 4, 5
Using an NIST traceable control solution with an exact osmolarity of 338 mOsm/L – indicative of a patient with moderately severe dry eye disease – TearLab measures accuracy and precision data on each of its instruments in the physician’s office. Each instrument is tested 10 times in a row with the high control solution. The results of 10-tests will provide (1) accuracy, or how close to the 338 mOsm/L target the instruments actual read, and (2) precision, or how variable the 10 measurements are from each other.
|N = 110||Number of instruments|
|Tests = 1067||Number of tests performed using high control solution|
|Mean = 338.0 mOsm/L||Average accuracy of all instruments combined|
|Bias = 0.0 mOsm/L||The error in measurement from the target value|
|Median = 338.6 mOsm/L||Fifty % of the instruments tested above this value and 50% tested below this value|
|SD = 3.4 mOsm/L||Standard Deviation, or the maxiumum variation (+/-) from the target value that would be seen in 68 out of 100 tests (1SD)|
|CV = 1.0%||Coefficient of Variation, or variability as a percentage between consecutive measurements|
In conclusion, of 110 instruments tested, the average reading was 338 mOsm/L – a zero bias from the target value, with an expected deviation from this target within ±3.4 mOsm/L 68% of the time (1SD) and ±6.8 mOsm/L 95% of the time (2SD). Fifty percent of the tests read above 338.6 mOsm/L and 50% read below that mark indicating a tight Gaussian distribution centered around the mean - with no greater risk of a test being above than below the target value. The expected variability from measurement to measurement is 1.0%.