You could be reading the full-text of this article now if you...

If you have access to this article through your institution,
you can view this article in

Diurnal Pattern of Tear Osmolarity and Its Relationship to Corneal Thickness and Deswelling

Niimi, Joycelyn OD; Tan, Bo PhD; Chang, Jenny BS; Zhou, Yixiu PhD; Ghanekar, Avanti OD; Wong, Michelle BS; Lee, Annie BS; Lin, Meng C. OD, PhD

Cornea:
doi: 10.1097/ICO.0b013e31829b21d1
Clinical Science
Abstract

Purpose: To identify the diurnal variations of tear osmolarity (TO) and its relationship with central corneal thickness (CCT) and corneal deswelling over a 14-hour period.

Methods: TO and CCT were measured using the TearLab Osmometer and Bioptigen spectral domain optical coherence tomography, respectively, on 38 healthy neophytes (mean age, 21.5 ± 2.2 years). TO and CCT were measured at bedtime (baseline), upon awakening, 20 minutes, 40 minutes, 1 hour, 2 hours, 4 hours, and 8 hours after awakening. Deswelling rate was estimated and expressed as percent recovery per hour (PRPH). Mixed-effect linear regression models describe the relationships among TO, CCT, and PRPH.

Results: The tear film upon wakening (264 ± 14 mOsm/L) was hypoosmotic compared with baseline (297 ± 15 mOsm/L, P < 0.001). TO (in mOsm/L) at 20 minutes, 40 minutes, 1 hour, 2 hours, 4 hours, and 8 hours were 287 ± 10, 292 ± 16, 293 ± 12, 292 ± 10, 289 ± 10, and 286 ± 10, respectively. CCT (mean ± SD) at baseline was 552.2 ± 35.9 µm and increased to 572.0 ± 38.7 µm after sleep. CCT returned to baseline thickness 4 hours after awakening (P < 0.000) and remained stable throughout the day. A small but statistically significant association was found between higher TO and lower CCT (P < 0.0001) and between lower baseline TO and higher PRPH (faster deswelling; P < 0.0001).

Conclusions: The diurnal pattern of TO has been established. The association of TO with corneal thickness and deswelling suggests that the tear film tonicity may be partly responsible for corneal hydration control; however, the effect may not be of clinical significance in a normal study cohort.

Author Information

Clinical Research Center, School of Optometry, University of California, Berkeley, CA.

Reprints: Meng C. Lin, Clinical Research Center, School of Optometry, University of California, Berkeley, CA 94720-2020 (e-mail: mlin@berkeley.edu).

Supported by unrestricted funds from UCB-CRC (University of California at Berkeley—Clinical Research Center) with contributions from the Sarver Foundation.

The authors have no conflicts of interest to disclose.

Received February 19, 2013

Accepted May 06, 2013

© 2013 by Lippincott Williams & Wilkins.