Corneal Biomechanics as a Function of Intraocular Pressure and Pachymetry by Dynamic Infrared Signal and Scheimpflug Imaging Analysis in Normal Eyes

PURPOSE: To evaluate corneal biomechanical deformation response using Ocular Response Analyzer (ORA) and Corvis ST data. DESIGN: Prospective observational case-control study. METHODS: A total of 1262 eyes of 795 patients were enrolled. Three groups were established, according to the corneal compensated intraocular pressure (IOPcc): Group I (10-13 mm Hg), Group 11 (14-17 mm Hg), and Group III (18-21 mm Hg). Each group included 3 subgroups, based on central corneal thickness (CCT): Subgroups 1 (465-510 mu m), 2 (510-555 mu m), and 3 (555-600 mu m). In addition, similar groups of CCT were divided into subgroups of IOPcc. Corneal hysteresis (CH) and corneal resistance factor (CRF) were derived from ORA. The parameters of highest concavity with the parameters of first and second applanation were recorded from Corvis ST. RESULTS: CH and CRF, applanation 1 time, and radius of curvature at highest concavity showed significant differences between CCT subgroups for each IOPcc group (P < .0001). CH, applanation 1 and 2 time, and applanation 2 velocity, as well as deformation amplitude (DA), showed significant differences by IOP subgroups for all CCT groups. IOPcc is correlated negatively with CH (r = -0.38, P < .0001). There are positive correlations of IOPcc with applanation 1 time, applanation 2 velocity, and radius and negative correlations with applanation 2 time (r = -0.54, P < .0001), applanation 1 velocity (r = -0.118, P < .0001), and DA (r = -0.362, P < .0001). CONCLUSION: ORA and Corvis ST parameters are informative in the evaluation of corneal biomechanics. TOP is important in deformation response evaluation and must be taken into consideration. (C) 2014 by Elsevier Inc. All rights reserved.