Assessment of the diurnal variation in central corneal thickness and intraocular pressure for patients with suspected glaucoma

Objective: To assess whether a single daily measurement using ultrasonic pa chymetry gives a representative assessment of mean central corneal thicknes s (CCT) in patients with suspected glaucoma and whether diurnal changes in CCT are related to diurnal variations in intraocular pressure (IOP). Design: Cross-sectional study. Method: Central CCT and IOP were measured by a single observer in 56 eyes o f 28 patients with suspected glaucoma using an ultrasonic pachymeter and a Goldmann tonometer, Four measurements were made over a 24-hour period: at 8 :00 AM, 12:00 PM, 4:00 PM, and 8:00 PM. Main Outcome Measures: Intraocular pressure and pachymetry. Results: Mean IOP was 19.80 mmHg at 8:00 AM (95% confidence interval [CI], 18.95-20.66 mmHg), 20.38 mmHg at 12:00 PM (95% Cl, 19.49-21.26 mmHg), 19.91 mmHg at 4:00 PM (95% CI, 19.99-21.83 mmHg), and 19.23 mmHg at 8:00 PM (95% CI, 18.35-20.11 mmHg). Mean CCT was 569.4 mu m (95% Ci, 560.2-578.7 mu m), 567.6 mu m (95% CI, 558.4-576.7 mu m), 569.1 mu m (95% CI, 559.5-578.6 mu m), and 567.2 mu m (95% CI, 557.9-576.4 mu m) at the four respective time p oints. There was no significant correlation between IOP and CCT in any pati ent (Pearson rank correlation coefficient); nor was there any significant c orrelation between the mean diurnal variations of IOP and CCT, Conclusions: In this group of patients with suspected glaucoma, there was n o significant variation in CCT, Therefore, a single measurement of CCT is s ufficient when assessing patients with suspected glaucoma. There was no cor relation between change of IOP and change of CCT. Ophthalmology 2000;107:11 91-1193 (C) 2000 by the American Academy of Ophthalmology.