Randomized comparison of in vivo performance of two point-of-care tear film osmometers

Abstract

PurposeTo compare the in vivo precision of two commercially available point-of-care osmometers among normal subjects with no dry eye disease.MethodsTwenty healthy adults with healthy ocular surfaces were evaluated by licensed eye care practitioners. All subjects had low Ocular Surface Disease Index score (<5), normal tear breakup time (>10 seconds), and no evidence of corneal fluorescein staining. Five consecutive measurements of tear osmolarity were measured on each eye using each of the two osmometers: the TearLab Osmolarity System (TearLab) and the I-Med i-Pen (i-Pen), for a total of 200 measurements per device. Performance of the osmometers was determined by specificity, estimated by the percentage of osmolarity data at or below the clinical cutoff (308 mOsm/L) and precision, and represented by the standard deviation per subject. In addition, to assess analytical performance, on each day of patient testing, standardized osmolarity quality control solutions (338 mOsm/L) were tested on the TearLab per manufacturer instructions. i-Pen manufacturer instructions do not neither provide for, nor recommend quality control procedures.ResultsThe mean age of the 20 subjects was 27±8 years (range: 19–48 years, 16 females, four males). Over 2 months of testing, the TearLab reported analytical performance on quality control solutions of 335.8±4.2 mOsm/L with a coefficient of variation of 1.3%. In the subject cohort, 90.9% of TearLab measurements were in the normal range ≤308 mOsm/L. The i-Pen reported 37.5% of all measurements in the normal range. The average intra-subject osmolarity of the TearLab was 295.4±8.6 mOsm/L, which was significantly lower and less variable than the i-Pen, which reported an average of 319.4±20.3 mOsm/L (P<0.001). When the measurements were grouped by subject, the TearLab accurately identified 100% of subjects as normal while the i-Pen accurately identified only 15% of subjects as normal.ConclusionIn this randomized comparative study of two point-of-care osmometers among normal, healthy non-dry eye subjects, the TearLab Osmolarity System demonstrated accuracy, precision, and agreement with clinical interpretation in line with the manufacturer claims. The i-Pen lacked sufficient performance to delineate subjects with and without dry eye disease.

Topical Low Dose Preservative-Free Hydrocortisone Reduces Signs and Symptoms in Patients with Chronic Dry Eye: A Randomized Clinical Trial

“…Tear film osmolarity was measured using a noninvasive, commercially available instrument (TearLab Ò , OcuSens Inc, San Diego, USA) at the indicated time points. Reproducibility of the instrument has been published previously [13,14].…”

Reproducibility in measuring tear samples using a freezing point depression osmometer

“…While repeated measurements over a period of time have been shown to be low and stable in normal subjects, DED subjects showed relatively elevated and unstable readings; indeed, the variability of osmolarity or increasing variation with increasing value is a statistical characteristic called heteroscedasticity and might be considered as a clinical indication of the loss of tear film homeostasis that occurs with dry eye . In this study, inter‐session reproducibility of Fiske 110 showed no differences between sessions or the correlation between the means and differences for both protocols.…”

“…Subjects were recruited among patients visiting the Optometry Clinic of the Optometry Faculty (Universidad de Santiago de Compostela) for an eye examination. As the aim of the study was to evaluate the inter‐session reproducibility of the protocol previously reported, only healthy volunteer subjects were recruited in order to avoid any interference of other possible variables in the analysis …”

Tear Film Osmolarity Measurement in Japanese Dry Eye Patients Using a Handheld Osmolarity System

“…Second, osmolarity measurements obtained using the I-PEN system may not be accurate, although Chan et al reported that the I-PEN system yielded rapid and accurate measurements of tear osmolarity in their “simulated testing setting” [ 23 ]. In contrast, some studies comparing different osmolarity measurement systems reported inferior repeatability of I-PEN measurements compared to those of other instruments [ 24 , 25 ]. It is possible that contact between the SUS of the I-PEN and the tarsal conjunctiva, even if extremely slight, may induce transient lacrimation, resulting in a decrease in tear osmolarity.…”