Influence of Corneal Hysteresis on Agreement Between Corneal-Compensated, Non-Contact, and Rebound Tonometry

Background/Objectives: Intraocular pressure measurements are influenced by corneal biomechanical properties, but their contribution to discrepancies between different tonometric methods remains poorly understood. This study evaluated the influence of corneal hysteresis (CH) on differences between corneal-compensated IOP (IOPcc), non-contact (NCT), and rebound tonometry, while adjusting for age and central corneal thickness (CCT). Methods: This cross-sectional study included 134 eyes. IOP was measured using NCT, iCare Pro rebound tonometry, and the Ocular Response Analyzer, which provided IOPcc and CH. Central corneal thickness was measured by spectral-domain optical coherence tomography. Agreement was assessed using regression-based Bland–Altman analysis. Multivariable linear regression evaluated CH, CCT, and age as determinants of the tonometric differences. Inter-method differences were also compared across CH tertiles. Results: Mean biases were +0.15 mmHg for IOPcc–NCT, +1.68 mmHg for IOPcc–iCare, and +1.18 mmHg for NCT–iCare. After adjustment for CCT and age, each 1-mmHg decrease in CH was associated with a 1.56-mmHg increase in the IOPcc–NCT difference and a 2.23-mmHg increase in the IOPcc–iCare difference (both p<0.001). Differences involving IOPcc progressively increased across decreasing CH tertiles. In the lowest CH tertile, the mean IOPcc–NCT difference was 2.50 ± 2.05 mmHg, whereas the mean IOPcc–iCare difference reached 5.51 ± 3.11 mmHg, indicating clinically relevant discrepancies in eyes with low CH. Conclusions: Lower corneal hysteresis was associated with greater discrepancies between biomechanically compensated and the other tonometric methods. While mean differences were small in the overall cohort, they became clinically relevant in eyes with low CH. These findings suggest that considering CH in addition to CCT may support a more accurate interpretation of IOP measurements in biomechanically vulnerable eyes.