Abstract
Purpose: :
To determine the variation of tear osmolarity and its relation to tear meniscus volume during office hours in dry eye patients and healthy controls.
Methods: :
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).
Results: :
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).
Conclusions: :
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.
Clinical Trial: :
http://www.clinicaltrials.gov NCT01206244
Keywords: cornea: tears/tear film/dry eye • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)