High myopes exhibited lower CH than emmetropes. Although CH had stronger correlation with FST than AL, it might contain the biomechanical properties of components other than the cornea.

Background:  This study investigated the use of corneal volume to monitor the corneal swelling response induced by wearing high plus power contact lenses. Methods:  Twelve young non‐contact lens wearers were recruited with one eye fitted with a soft contact lens (Polymacon material, 38.6 per cent water, Dk of 9 and 0.27 mm centre thickness) and the fellow eye served as control. The treated eye was patched for two hours leaving the control eye uncovered. Central corneal thickness (CCT) was measured with non‐contact specular microscopy and corneal volumes (at three, five and 10 mm zones) were measured with a corneal topographer (Pentacam, Oculus Inc, Germany), before eye patching as well as immediately after and every 20 minutes for 100 minutes. Results:  Subjects had similar CCT and corneal volumes between the two eyes before treatment. The treatment eyes showed a mean corneal swelling of 8.1 per cent immediately after lens removal. Corneal volume was significantly increased at the three (mean swelling of 5.9 per cent), five (5.6 per cent) and 10 millimetre (3.3 per cent) zones. It took 20 minutes for the corneal volume at the 10 mm zone to return to baseline but required 60 minutes for the three and five millimetre zones to return to the baseline level. The central corneal thickness was still significantly thicker 80 minutes after patching. Conclusion:  Corneal volume could be a useful parameter to monitor corneal change when an event affects the entire cornea. Corneal volume combined with central corneal thickness could give more comprehensive information to monitor central corneal swelling.

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.

The interobserver variation in corneal sublayer pachymetry could be improved by having the observers going through some corneal frames together rather than just following the written criteria. The use of CS4 (z ring) to measure CT, FST, and Epi+BT is suitable for monitoring corneal changes clinically.