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Ryan A. Vasan, Thomas L. Berenberg, Christopher E. Starr; Correlation of Tear Osmolarity and Ocular Surface Disease Index Scores in Healthy Volunteers. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3794.
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Clinical assessments of Dry Eye Disease (DED) severity have relied on a combination of subjective measurements (symptom questionnaires) and objective measurements (tear film breakup time, corneal and conjunctival staining and Schirmer’s testing) which tend to have a high level of inter-operator variability. TearLab, a recently available tear osmolarity device, provides an objective assessment of DED severity with significantly less inter-operator variability when compared to traditional measures. A prospective, single-site clinical study was performed comparing a commonly used subjective symptom questionnaire to a point-of-care measure of tear osmolarity in assessing dry eye symptoms in a group of healthy volunteers.
60 consecutive subjects were recruited on a voluntary basis under an IRB-approved protocol. All qualified subjects completed the Ocular Surface Disease Index (OSDI), a 12-question survey assessing dry eye disease symptoms in the last week, as well as bilateral tear osmolarity measurements using the TearLabTM device. OSDI scores were correlated to the higher of two osmolarity measurements (one from each eye) using raw data as well as by segregation into quartiles.
(preliminary data) The average OSDI survey score was 11.93 out of 100 with a range of 0 to 47.9, and the mean osmolarity measurement was 320mOsm/L, with a range of 297-342. Comparing raw data yielded a correlation coefficient of 0.32, and using categorization into quartiles separating OSDI from 0-12, 13-30, 31-45, and greater than 45 and osmolarity into 275-308, 308-324, 235-364, and greater than 365, yielded a correlation coefficient of 0.42.
DED is a prevalent disorder affecting tens of millions of Americans with far reaching consequences concerning visual acuity and quality of life. It is well known that patient symptoms in DED are often poorly correlated to clinical findings on exam. We sought to evaluate the correlation of tear osmolarity, as measured by a novel in-office device (TearLab), against a widely accepted subjective survey-based assessment of patient symptoms (OSDI). Initial data shows a weak correlation between the objective osmolarity measurement and the subjective questionnaire, furthering the disparity between signs and symptoms in DED. A weakness of our study is the inclusion of healthy volunteers who do not necessarily have DED, however, high osmolarity in the absence of dry eye symptoms may be indicative of early pre-clinical DED.
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