Background: To evaluate the inter- and intraobserver variability of ocular response analyzer (ORA) measurements, namely corneal-compensated intraocular pressure (IOPcc), corneal resistance factor (CRF) and corneal hysteresis (CH).
Methods: One randomly chosen eye of 46 healthy volunteers was included in this study. Three clinical observers performed three consecutive measurements using ORA, with an interval of 1-2 minutes between measurements. In all subjects, central corneal thickness (CCT) was measured. The inter- and intraobserver reproducibility for IOPcc, CRF and CH was assessed by ANOVA-based intraclass correlation coefficient (ICC) and coefficient of variation (CV).
Results: The mean ICC for interobserver reproducibility was 0.94 for IOPcc, 0.90 for CRF, and 0.86 for CH. The corresponding CV values were 12.8%, 10.3%, and 13.6% respectively. The intraobserver ICC values for IOPcc were 0.86 for the first examiner, 0.84 for the second, and 0.89 for the third. CV was 11.7%, 11.9%, and 11.0% respectively. For CRF, the intraobserver ICC values were 0.69, 0.81, and 0.63, and corresponding CV values were 9.6%, 8.1, and 10.8%. The intraobserver ICC for CH was 0.66 for the first observer, 0.71 for the second, and 0.61 for the third examiner. The respective CV values were 12.7%, 11.8%, and 13.9%. There was a significant correlation between CCT and CRF (Rsq = 0.13, p = 0.02). The correlations of CCT with IOPcc and CH were not significant (p > 0.05).
Conclusions: The interobserver reproducibility of ORA measurements was almost perfect for IOPcc, CRF, and CH. The intraobserver short-term reproducibility was almost perfect for IOPcc and substantial for CRF and CH, for all observers. The significant correlation between CCT and CRF, and no association between IOPcc and CCT, are in agreement with previous studies. There was no significant correlation between CH and CCT in our study. This device might be useful in glaucoma diagnosis and management.