To determine whether there is a temporal relationship between the diurnal variation of central corneal thickness (CCT) and intraocular pressure (IOP) by Goldmann applanation tonometry in young normal human participants in vivo.
Twenty-five eyes of 25 young healthy normal participants were examined in a prospective observational cross-sectional study. IOP, CCT and corneal curvature were measured using standard clinical techniques over a 24-hour period, and the temporal interrelationships between these parameters were examined.
The overnight change in IOP measured by Goldmann tonometry was 3.1±2.4 mm Hg (P<0.001), CCT was 20.1±10.9 μm (P=0.016), with no statistical change in central corneal curvature (0.05 mm, P=0.477, paired t test with Bonferroni correction). Both IOP and CCT were highest on awakening at 7:00 then dropped rapidly to baseline levels by 9:00 (linear mixed models), and these two parameters were highly correlated (r=0.978, P<0.001). After 9:00, there was no correlation between these parameters (r=−0.453, P=0.260).
The results of this study have highlighted a potential link between the diurnal variation of CCT and the accuracy of Goldmann tonometry estimates of IOP during the first 2 hours after awakening. Clinicians should be wary of using Goldmann tonometry to estimate IOP until the overnight increase in CCT has resolved.
School of Optometry and Vision Science, University of New South Wales, Sydney NSW 2052, Australia
Reprints: David Cecil Pye, M. Optom, School of Optometry and Vision Science, Level 1, North Wing, Rupert Myers Building, University of New South Wales, Sydney NSW 2052, Australia (e-mail: email@example.com).
Received for publication May 10, 2006; accepted October 10, 2006
Sources of support: None.
Prior publication: The information contained in this article was published in part at the ARVO meeting in Florida, 2005.
Pye DC, Hamilton KE, Aggarwala S, et al. Diurnal variation of corneal thickness and its effects on intraocular pressure estimates by Goldmann tonometry. IOVS EAbstract 2005;46:4857.
Conflict of interest, financial disclosure: No author has any professional or personal relationships that may result in a conflict of interest.