Ocular response analyzer versus Goldmann applanation tonometry for intraocular pressure measurements

PURPOSE. To establish correlations between intraocular pressure (IOP) measurements obtained with the ocular response analyzer (ORA) and the Goldmann applanation tonometer ( GAT). The effects of central corneal thickness on the measures obtained were also examined. METHODS. This was a cross-sectional study. IOP was determined in 48 eyes of 48 patients with glaucoma In all patients, central corneal thickness (CCT) was measured by ultrasound pachymetry. RESULTS. ORA readings were consistently higher than GAT measurements (Goldmann-correlated IOP-IOP GAT mean difference, 7.2 +/- 3.5 mm Hg; corneal-compensated IOP-IOP GAT mean difference, 8.3 +/- 4.0 mm Hg) However, differences were not constant and increased with increasing IOP GAT readings, both with respect to Goldmann-correlated IOP (slope = 0.623, P < 0.0001) and corneal- compensated IOP (slope = 0.538, P < 0.0001). Both pressure measurements provided by the ORA showed significant correlation with CCT (CCT versus Goldmann-correlated IOP: r = 0.460, P = 0.001; CCT versus corneal- compensated IOP: r = 0.442, P = 0.001). No significant effects of corneal curvature or refraction on any of the pressures were observed. CONCLUSIONS. The ORA significantly overestimates IOP compared with the GAT. Differences between both sets of measures increase as the GAT-determined IOP increases. ORA readings seem to be affected by central corneal thickness.