The relationship of tear osmolarity with tear meniscus curvature and contact angles in healthy subjects: anterior segment optical coherence tomography study.

PURPOSE To evaluate the relationship of tear osmolarity (TO) with tear meniscus curvature and contact angles by anterior segment optical coherence tomography (AS-OCT) in healthy subjects. METHODS The right eyes of 64 consecutive healthy subjects were included in the study. The eyes were scanned by AS-OCT for the measurements of upper and lower tear menisci. The geometrical components of the upper and lower menisci, including height, depth, area, and radius of the menisci, cornea-meniscus angle (α-angle), meniscus-eyelid angle (β-angle), and curvature angle (θ-angle) were measured. TO was obtained by TearLab. All participants were administered Ocular Surface Disease Index questionnaires (OSDI), and tear film break-up time (TBUT), Schirmer I and II test measurements were also performed. RESULTS There was no association of TO with height, depth, and area of both menisci while TO was negatively correlated to θ-angle and radius of the lower eyelid meniscus (r = - 0.41, P < 0.001 and r = - 0.40, P < 0.01, respectively). The θ-angle and the radius of the lower meniscus were also significantly associated with OSDI score, TBUT, Schirmer I and II (P < 0.01 for all). There was a statistically strong correlation between the θ-angle and the radius of the lower meniscus (r = 0.91, P < 0.001). CONCLUSION The curvature angle and radius of the lower meniscus are significantly associated with TO. The curvature angle of the lower meniscus is a useful non-contact measure that may provide information indirectly about the osmolarity and the quality of the tear.