The Relationship of Tear Osmolarity With Tear Meniscus Curvature and Contact Angles in Healthy Subjects: Anterior Segment Optical Coherence Tomography Study

Abstract

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 (alpha-angle), meniscus-eyelid angle (beta-angle), and curvature angle (theta-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 theta-angle and radius of the lower eyelid meniscus (r = - 0.41, P < 0.001 and r = - 0.40, P < 0.01, respectively). The theta-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 theta-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.