Influence of corneal astigmatism, corneal curvature and meridional differences on corneal hysteresis and corneal resistance factor

Abstract

Background: This study investigated the influence of corneal astigmatism, corneal curvature and meridional differences on corneal hysteresis (CH) and the corneal resistance factor (CRF) in a group of normal Chinese persons. Methods: Ninety-five participants were recruited and data from the eye with higher corneal astigmatism were analysed. The anterior corneal curvature was measured by corneal topography. The Goldmann-correlated intraocular pressure (IOPg), cornealcompensated intraocular pressure (IOPcc), CH and CRF at different meridians (default horizontal position, 10°, 20°and 30°along the superotemporal and inferonasal meridians) were obtained from an ocular response analyser. The corneal powers at these specific meridians also were calculated. Results: At the default position, the IOPg and CRF had weak correlations with corneal astigmatism, while the IOPcc and CH were not significantly correlated with corneal astigmatism. Both the IOPg and IOPcc were measured significantly higher at the default position. The CH and CRF were lower at the default position but the difference in the CRF from obliquity could not reach statistical significance. The CH was not significantly correlated with the corneal power at all meridians. The CRF correlated with the corneal power only at 30°superotemporal. Conclusion: Corneal astigmatism and head tilt did not have much effect on the measurement of CH and the CRF, both of which were lowest along the horizontal meridian. Clinically, the difference was small. The influence of corneal power on CH and the CRF was minimal.

High myopes have lower normalised corneal tangent moduli (less ‘stiff’ corneas) than low myopes

“…Previous studies have reported that corneal toricity did not affect CH and CRF measurements . Despite the significant difference in corneal toricity between the two refractive groups, no association was observed between corneal stiffness and toricity.…”

Factors Influencing Efficacy of Peripheral Corneal Relaxing Incisions during Cataract Surgery

“…However, no correlation between corneal astigmatism and viscoelastic properties was found in this study and these results are in line with previous findings [ 23 ].…”

Relationship among Corneal Biomechanics, Anterior Segment Parameters, and Geometric Corneal Parameters

“…Kamiya et al reported similar result; they did not find any correlation between mean K value and CH and CRF in 86 eyes of 43 patients with a mean age of 39 years [3]. Wong and Lam found no correlation between mean K and CH and CRF in Chinese adults [9]. However, 2 different studies from Far East reported contradictory results.…”

“…Hwang et al found that corneal volume was positively correlated with CH, but not CRF [20]. Wong and Lam reported positive correlation both with CH and CRF [9]. In a recent study both CH and CRF were found to be correlated positively with CC and CV for the normal, keratoconic, and crosslinked eyes [22].…”