Diurnal variation of central corneal thickness and Goldmann applanation tonometry estimates of intraocular pressure.
OBJECTIVE
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.


METHODS
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.


RESULTS
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 mum (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).


CONCLUSIONS
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.
Hamilton
Kirsten Elizabeth
KE
School of Optometry and Vision Science, University of New South Wales, Sydney NSW 2052, Australia.
Pye
David Cecil
DC
Aggarwala
Shivani
S
Evian
Sindy
S
Khosla
Joti
J
Perera
Rachithri
R
D000293:Adolescent; D000328:Adult; D000886:Anthropometry; D002940:Circadian Rhythm / Q000502:physiology*; D003315:Cornea / Q000033:anatomy & histology*; D003430:Cross-Sectional Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D011446:Prospective Studies; D014065:Tonometry, Ocular