The corneal volume and biomechanical corneal factors: Is there any correlation?

BACKGROUND: The aim of this study was to determine the correlation between corneal hysteresis (CH) and the corneal resistance factor (CRF), which are both novel methods of analyzing ocular rigidity/elasticity, and various corneal characteristics, mainly corneal volume in normal subjects. METHODS: This cross-sectional study included 500 normal eyes of volunteers. An ocular response analyzer (ORA) was used to measure CH and CRF. Patient age and the Pentacam-measured corneal volume (CV), posterior elevation, anterior elevation, corneal curvature, central corneal thickness (CCT), corneal thickness of apex (CTA), and corneal thinnest thickness (CTT) were compared with CH and CRF. Statistical significance was defined at p < 0.05. RESULTS: The mean CH and CRF for all eyes were 9.9 ± 1.4 mmHg and 10.1 ± 1.6 mmHg, respectively. The mean CVs of the 3, 5, 7, and 10 mm zones for all eyes were 3.8 ± 0.2 mm3, 11.2 ± 0.6 mm3, 24.3 ± 1.4 mm3, and 60.1 ± 3.5 mm3, respectively. The correlations between CV and the hysteresis or CRF were significant in all zones. The CV of the 7-mm zone had the strongest correlation with CH (r = 0.438) and the CV of the 5-mm zone had the strongest correlation with CRF (r = 0.574). CONCLUSIONS: CH and CRF correlate with CV. Moreover, the correlation between CV and CRF is stronger than that between CV and CH. The CV may be valuable for determining patient's qualification for and predicting the outcome of refractive surgery. It would also be helpful in other cases in which corneal biomechanics are important.