Effect of supine body position on central corneal thickness

Background: To evaluate the effect of supine body position on central corneal thickness (CCT) in open-angle glaucoma patients and in healthy subjects. Design: A cross-sectional study at a university eye clinic. Participants: Twenty-three subjects were recruited in each group, for a total of 46 patients. Methods: CCT was measured using an ultrasound pachymeter in each subject. Three consecutive measurements in each eye were first taken in the sitting position, and repeated after 10 min and 30 min in a supine position. Results were analyzed using mixed model repeated measures, which adjusted for age, gender and laterality of eyes. Main Outcome Measures: CCT. Results: In healthy subjects, CCT decreased with supine positioning at 10 min (mean = −5.2 µm, P = 0.0043) and at 30 min (mean = −6.5 µm, P < 0.0001). In the glaucoma group, CCT decreased with supine positioning at 10 min (mean = −6.7 µm, P = 0.0043) and at 30 min (mean = −10.2 µm, P < 0.0001). There was no statistically significant difference between the CCT at 10 min supine and at 30 min supine in the healthy subjects (P = 0.37) and glaucoma patients (P = 0.14). CCT was shown to decrease linearly over time (P < 0.0001), and the slopes were not statistically different between groups (P = 0.40). Conclusions: CCT is a dynamic measurement that can be influenced by body position. It decreases linearly in the first 30 min of supine positioning at a similar rate in both open angle glaucoma patients and in healthy subjects.