Osmolarity Testing Systems Produce Similar Results for Patients With High BMI

Osmolarity scores were similar across devices, but 1 may have superior diagnostic accuracy for all patients.

Tear osmolarity measurements using the TearLab™ (Tearlab) and I-Pen® (I-Med Phrama) systems are strongly correlated with each other in individuals with high body mass index (BMI) and control individuals, but were significantly different between the systems in both groups of participants, according to research published in Advances in Clinical and Experimental Medicine.

Researchers prospectively evaluated the correlation of osmolarity measurements between 2 commonly used osmometers for the diagnosis and classification of dry eye disease (DED) — the TearLab and I-Pen systems — in study participants with a high BMI (27–48 kg/m2) as well as control individuals (BMI <24.9 kg/m2).

The study included 30 men in the high BMI group (mean age, 23.3±2.1 years) and 30 men in the control group (mean age, 22.9±2.1 years). The researchers recorded osmolarity measurements from the right eye of each participant using each system. They also interviewed all participants to determine ocular surface disease index (OSDI) scores.

In the high-BMI group compared with the control group, the investigators observed significantly higher OSDI (median, 8.0 vs 6.3; P =.042), TearLab (295.5 vs 287.0 mOsm/L; P <.001) and I-Pen (318.5 vs 298.5 mOsm/L; P <.001) scores. 

Osmolarity measurements using both I-Pen and Tear-Lab systems indicated that high BMI could induce DED.

They reported the range of osmolarity scores was 278-309 mOsm/L with TearLab and 294-336 mOsm/L with the I-Pen in the high-BMI group and, in the control group, from 263-304 mOsm/L with TearLab and 278-317 mOsm/L with the I-Pen. 

The team observed a strong correlation between the TearLab and I-Pen osmolarity scores in the high-BMI group (r=0.934; P =.001). They also observed strong correlations between BMI and both TearLab scores (r=0.736; P =.001) and BMI and I-Pen scores (r=0.707; P =.001) as well as between OSDI and TearLab scores (r=0.731; P =.001) and OSDI and I-Pen scores (r=0.666; P =.001).

“The current study suggests that osmolarity measurements using both the TearLab and I-Pen systems are strongly correlated to each other in subjects with high BMI. However, the I-Pen scores were significantly higher than the TearLab scores,” concluded the researchers. “Osmolarity measurements using both I-Pen and Tear-Lab systems indicated that high BMI could induce DED.”

Limitations of the study included the small sample size, recruitment of only younger men as participants, a single osmolarity measurement, lack of assessment of the order of use of the osmolarity systems, and the single-center study design.


Alanazi MA, El-Hiti GA, Alhafy N, et al. Correlation between osmolarity measurements using the TearLab™ and I-Pen® systems in subjects with a high body mass index. Adv Clin Exp Med. 2022;31(12):1413-1418. doi:10.17219/acem/156645