Frequently Asked Questions

TearLab is not currently aware of any differences in collection technique that affect osmolarity readings.

TearLab is not currently aware of any differences in collection location that affect osmolarity readings. TearLab recommends that tears be collected from the inferior lateral tear meniscus.

The single-use Test Card contains a microfluidic channel that is gently placed on the tear lake (meniscus) in the corner of the eye on the inner lower lid margin, and via passive capillary action, less than 50-nanoliters of tear sample is instantly and automatically collected when it comes in contact with tear fluid.

It is a calibration code that needs to be entered into the Reader after the sample has been collected and the Pen is docked into the Reader.

The solutes and biological components from the previous tear fluid sample will remain in the microfluidic channel and will result in an inaccurate measurement if used more than once. Due to the small size of the microfluidic channel, the Test Card cannot be cleaned after use.

The TearLab Test Card is a highly precise component, and even the smallest trace of residual salts will affect subsequent measurements. You should never collect tears with a used Test Card.

A Test Card without a protective cover should never be placed on a Pen or used to collect tears. Test Cards should be discarded immediately following a completed test result.

The Pen detects whether there is fluid within a Test Card to protect against re-use. If a Test Card is allowed to completely dry out, the Pen may illuminate; however, the Test Card will retain solutes and biological components from the previous tear fluid collection and will result in an inaccurate measurement if used more than once. You should never collect tears with a used Test Card.

CV (Coefficient of Variation) is an industry standard measurement of precision equal to the standard deviation divided by the mean of a set of measurements.

Sensitivity is the ability to diagnose persons who actually have the disease.

Specificity is the ability to diagnose persons who do not have the disease.

Positive Predictive Value is the percent of people with a positive test who have the disease.

Negative Predictive Value is the percent of people with a negative test who do not have the disease.

The TearLab Osmolarity System has demonstrated performance equivalent to existing laboratory osmometers. The historical performance of osmolarity in published literature is compared to published data on TearLab performance.

(ref: BD Sullivan et al. "Diagnostic performance of osmolarity combined with subset markers of dry eye disease in an unstratified patient population," ARVO 2010.).

Dry eye is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.
"The Definition and Classification of Dry Eye Disease: Report of the Definition and Classification Subcommittee of the International Dry Eye Workshop" The Ocular Surface,
2007;5(2):75-92, (DEWS Report)

a. Tear hyperosmolarity is regarded as the central mechanism causing ocular surface inflammation, damage, and symptoms, and the initiation of compensatory events in dry eye. Tear hyperosmolarity arises as a result of water evaporation from the exposed ocular surface, in situations of a low aqueous tear flow, or a combination of these events. TearLab has been shown to be able to measure osmolarity in physician office sites comparable to a reference laboratory osmometer with a correlation of r2 = 0.95.

b. The FDA has cleared the TearLab Osmolarity System "to measure the osmolarity of human tears to aid in the diagnosis of dry eye disease in patients suspected of having dry eye disease, in conjunction with other methods of clinical evaluation."

Normal osmolarities are typically found at a mean value of 302 mOsms/L, mild/moderate osmolarity (Dry Eye) at a mean of 315 mOsms/L and severe osmolarity (Dry Eye) at a mean of 336 mOsms/L. Osmolarity values in the low end of the abnormal range should be considered together with symptoms for a definitive dry eye diagnosis. Values in the upper range of normal (for the general population) e.g. 308-315, in the presence of symptoms should suggest early/mild DED.

In DED, it is known that symptoms correlate poorly with objective signs. It is important to note that in the absence of symptoms the presence of hyperosmolarity is still evidence of DED. Hyperosmolarity in the absence of symptoms should be considered an abnormality in the body's homeostatic osmoregulation and a sign of DED.

DED is a chronic and progressive disease. The TearLab Osmolarity System can aid in the diagnosis of early and late stage disease. Abnormal (or Dry Eye) values can increase to the mild/moderate range (with a mean value of 315 mOsm/L) to the severe range (with a mean value of 336 mOsm/L). Studies are currently ongoing to establish the relationship between disease progression and increasing osmolarity values.

The osmolarity value will be a composite of the combined effects of either dysfunction (aqueous deficiency or evaporative) and should be used in a global assessment of dry eye disease. The ultimate endpoint of disease progression is a hyperosmolar state.

Hyperosmolarity plays a role in the physical destabilization of the tear film, damage to the ocular surface and the physiological progression of the disease. It is recognized as both a sign of the disease and the central causative mechanism in the disease pathogenesis.

There is no known relationship between the osmolarity of other body fluids and tear fluid. However, studies are currently ongoing to better define this relationship.