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Ming Li, Chixin Du, Dexi Zhu, Meixiao Shen, Jianhua Wang; Variation of Tear Osmolarity and Its Relation to Tear Meniscus Volume Over Office Hours. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3795.
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To determine the variation of tear osmolarity and its relation to tear meniscus volume during office hours in dry eye patients and healthy controls.
In this pilot study, 10 clinically diagnosed dry eye patients (4 males and 6 females, age 36 ± 12 yrs) and 10 normal subjects (5 males and 5 females, age 27 ± 7 yrs) were enrolled. The tear meniscus volume was measured with ultra-high resolution optical coherence tomography (OCT) and tear osmolarity was measured using TearlabTM Osmolarity system. Both measurements were conducted every two hours from 8:30am to 4:30pm. The OCT imaging was performed first, followed by the tear osmolarity test. Diagnosis of dry eye was based on signs and symptoms (OSDI > 12 and TBUT < 10 seconds or Schirmer < 5 mm).
At screening, the OSDI score was 37 (SD 20) in the dry eye group, which was significantly higher than that in the healthy group (3 ± 3, mean ± SD, P < 0.01). The average osmolarity was 299.8 mOsms/L (SD 11.5) for dry eye patients and 296.6 (SD 13.3) for normals. Upon repeated measures over the course of 8 hours, the osmolarity score of a single individual varied from 6 to 43 in the dry eye group (mean variation 18.6, SD 12.8) and from 8 to 35 in normals (mean variation 20.2, SD 8.7). Differences in total tear volume as measured by OCT were found between two groups at the last three time points (post hoc, P < 0.05). No correlations were found between tear meniscus volumes and tear osmolarity in any of these two groups (r was 0.03 for dry eye group and -0.005 for healthy group, P > 0.05).
Variations in osmolarity scores for individual dry eye and normal patients were documented for the first time over the course of 8 hours during office hours. Based on the TearLab recommended cut-off for determining dry eye (308), the tear osmometer may under diagnose dry eye as shown in this study.
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