Repeatability of corneal biomechanical measurements in children wearing spectacles and orthokeratology lenses

Abstract

To determine the repeatability of corneal hysteresis (CH) and corneal resistance factor (CRF) measurements in children wearing spectacles and children under orthokeratology (ortho-k) therapy using the Ocular Response Analyzer (ORA). CH and CRF were measured twice at a 10-min interval using ORA on the same day in both eyes of 25 children (mean age = 10.6 ± 1.2 years) wearing spectacles and 34 children (mean age = 10.9 ± 1.0 years) wearing ortho-k lenses. Four measurements were obtained from each eye in each set of measurements. Only data from the right eyes were analyzed. No significant between-measurement differences in CH and CRF were found in either group of subjects (paired t-tests, p > 0.05) and no correlations were found between the mean differences and their means (Pearson's correlations, -0.09 < r < 0.21, 0.24 < p < 0.85). The 95% limits of agreement (LA) were -1.87 mmHg to +2.59 mmHg and -1.53 mmHg to +1.41 mmHg for CH and -1.86 mmHg to +2.22 mmHg and -1.45 mmHg to +1.57 mmHg for CRF in the spectacle and ortho-k groups, respectively. A significant between-group difference in CRF was found (unpaired t-tests, p = 0.02). Repeatability of CH and CRF measurements using the ORA is within ± 2 mmHg in children wearing spectacles or ortho-k lenses. We suggest that the ORA can be used to monitor long-term corneal biomechanical changes during ortho-k treatment.