Can CCT and its fluctuations influence the amount of circadian intraocular pressure fluctuations?

Purpose:To evaluate the influence of central corneal thickness (CCT) and its 24-hr fluctuations on nicthoemeral intraocular pressure (IOP) fluctuations in glaucoma subjects. Methods:36 consecutive patients (age: 67±8 years; F/M=17/19) with primary open-angle glaucoma underwent circadian evaluation (8 pm, midnight, 4 am, 8 am, noon, and 4 pm) of supine and sitting IOP, measured with a handheld Perkins and a Goldmann tonometer respectively, and of CCT measured using an ultrasonic pachymeter. 30 patients were treated with timolol 0.5% twice daily (8 am, 8 pm) and latanoprost 0.005% once daily (9 pm); 6 patients were untreated. Individual fluctuations were calculated as the standard deviation over the 24-hr curves. The correlations between CCT and its fluctuations and IOP fluctuations were evaluated by means of regression analysis. Results:The correlation between mean CCT and CCT fluctuations and IOP fluctuations was not statistically significant both at supine (y=6.38, P=0.92 and y=-0.04x+7.66, P=0.57 respectively) and sitting position (y=0.02x-5.61, P=0.06 and y=-0.04x+5.92, P=0.51). No differences were found between treated and untreated patients (P=0.27). Conclusions:In the present study, 24-hr IOP fluctuations were independent from mean CCT values and their 24-hr fluctuations both in treated and untreated glaucoma patients.