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

Abstract

Objective To assess whether a single daily measurement using ultrasonic pachymetry gives a representative assessment of mean central corneal thickness (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 of 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% CI, 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 μm (95% CI, 560.2–578.7 μm), 567.6 μm (95% CI, 558.4–576.7 μm), 569.1 μm (95% CI, 559.5–578.6 μm), and 567.2 μm (95% CI, 557.9–576.4 μm) at the four respective time points. There was no significant correlation between IOP and CCT in any patient (Pearson rank correlation coefficient); nor was there any significant correlation between the mean diurnal variations of IOP and CCT. Conclusions In this group of patients with suspected glaucoma, there was no significant variation in CCT. Therefore, a single measurement of CCT is sufficient when assessing patients with suspected glaucoma. There was no correlation between change of IOP and change of CCT.