Evaluation of corneal biomechanical properties with the Reichert Ocular Response Analyzer

To compare corneal hysteresis (CH) and corneal resistance factor (CRF) measured with the Ocular Response Analyzer (ORA) in patients with primary open-angle glaucoma (POAG), patients with ocular hypertension (OHT), and normal subjects (NL); and to assess correlations of CH and CRF with corneal-compensated intraocular pressure (IOPcc), Goldmann applanation tonometry (GAT), glaucoma type, central corneal thickness (CCT), previous filtering procedure, and antiglaucoma medications.

A total of 108 POAG, 22 OHT, and 24 NL were enrolled in this observational study. Goldmann applanation tonometry and ORA were performed in a randomized sequence followed by pachymetry. One eye per subject was selected at random for analysis. Chi-square, Wilcoxon, and Kruskal-Wallis tests were used for comparison and Spearman coefficient for assessing correlations.

Mean CH and CRF were significantly lower in POAG than in OHT and NL. Ocular Response Analyzer IOPcc overestimated IOP compared to GAT only in POAG. This difference increased with higher GAT. Goldmann applanation tonometry and IOPcc were correlated. Corneal hysteresis was negatively correlated with age in POAG. Corneal resistance factor and CH were positively correlated with CCT in POAG and OHT. Unlike CRF, CH was not correlated with GAT in POAG and OHT. Corneal-compensated intraocular pressure was not correlated with CCT. Difference between GAT and IOPcc was not CCT dependent. Corneal hysteresis and CRF were comparable in POAG and NTG, unchanged after filtering procedure. Corneal hysteresis was not altered by topical medications. Corneal resistance factor was significantly lower in treated eyes and those receiving prostaglandin analogues with no correlation with the treatment duration.

Patients with glaucoma seem to have distinctive corneal biomechanical properties compared to OHT and NL. They may be influenced by many other unknown subparameters.