Correlation of corneal hysteresis and central corneal thickness with intraocular pressure measured by ocular response analyzer and goldmann applanation tonometer

Background: Ocular response analyzer (ORA) is a unique tonometer which can measure intraocular pressure (IOP) independent of corneal properties. In this study, we compared the corneal compensated IOP (IOPcc) as measured by ORA with IOP measured by Goldmann applanation tonometry (GAT) and the influence of corneal hysteresis (CH) and central corneal thickness (CCT) on IOP measurement. Setting and Design: This was an observational cross-sectional study. Methods: This study was conducted on 176 eyes of 88 patients aged 23–77 years. A full ophthalmic examination including GAT, IOPcc, CH, and CCT was obtained. Exclusion criteria included previous intraocular surgery, refractive surgery, glaucoma, or any other intraocular disease. Statistical Analysis: Windows SPSS software was used, and the level of significance was taken as P < 0.05. Results: The mean (± standard deviation [SD]) IOP with GAT was 16.9 mmHg (±4.04) (range: 5.8–30 mmHg). The mean (±SD) IOPcc was 18.0 mmHg (±4.49) (range: 10–41.6 mmHg), the mean (±SD) CH was 10.1 (±1.17) (range: 6.1–16.9), and the mean CCT (±SD) was 528.11 μm (38.75) (range: 451–644 μm). The mean difference between IOP GAT and IOPcc (±SD) was 1.1 mmHg (±5.87), which was statistically significant. However, there was no correlation between IOP GAT and IOPcc. None of the methods correlated with CH and CCT. Conclusion: IOP readings with ORA were higher than GAT, with no significant correlation between them. To date, it is not clear regarding the impact and association of CH on IOP measurement.