Purpose:
Corneal hysteresis (CH) has been shown to correlate with glaucoma progression. In this study, we sought to determine the amount of variation in CH accounted for by intraocular pressure (IOP) and other predictive variables.
Methods:
We retrospectively analyzed records from 324 consecutive patients with open-angles under evaluation for glaucoma and without evidence of non-glaucomatous visual field loss. Patients underwent CH measurement using the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY), Goldman applanation tonometry (GAT), and ultrasound pachymetry (DGH Technology, Exton, Pennsylvania) followed by a dilated full ophthalmic exam between June and November 2009. Patients’ right eyes were included unless data was unavailable, in which case the left eye was used. Simple and multiple linear regression models were constructed to determine the R-squared value corresponding to the variance in the dependent variable accounted for by the predictor(s).
Results:
Although there was a significant linear relationship between GAT and CH, GAT accounted for only about 1% of the variance in CH (p<0.05). As expected, CH was most dependent on central corneal thickness (CCT; R''=0.28; p<0.001) and ORA generated corneal-compensated IOP (R''=0.25; p<0.001). A maximum of 36% of the variability in CH was accounted for by the combined predictive value of GAT, CCT and age. Partitioning patients by treatment status, we observed only clinically insignificant changes in the relationship between CH and independent variables (Table).
Conclusions:
The finding that CCT, GAT, and age together accounted for only 36% of the variability in CH suggests that CH may represent a unique corneal property or vulnerability to glaucoma independent of these variables. We emphasize that the cross-sectional and longitudinal dependencies of CH on IOP may be distinct.1. Congdon NG, et al. Am J Ophthalmol. 2006;141:868-75.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology