A Clinical Description of Ocular Response Analyzer Measurements

PURPOSE: To examine the interrelationships among the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY), Goldmann applanation tonometer (GAT), and corneal geometry measurements in a young, healthy sample. METHODS: Central corneal radius, ORA, GAT, and central corneal thickness (CCT) measurements were taken in 99 subjects (age, 21 ± 2 years) who were free of ocular and systemic disease. RESULTS: The mean ± SD corneal hysteresis (CH) and corneal resistance factor (CRF) were 10.4 ± 1.2 and 10.1 ± 1.5 mm Hg, respectively. The Bland-Altman 95% limits of agreement of ORA Goldmann-correlated IOP (ORAg) and ORA corneal-compensated (ORAcc) IOP with reference to GAT were -4.5 to +6.0 and -4.1 to +6.8 mm Hg, respectively. The full equations used by the ORA to calculate ORAcc and CRF were reconstructed. The statistically significant effect of CCT on GAT became redundant if CRF was included in a multivariate regression analysis. Both CH and CRF were associated with CCT (R(2) = 0.252 and 0.290, respectively). CONCLUSIONS: Sample CH and CRF were consistent with those reported in the literature. ORAg and ORAcc agreed poorly with GAT. CRF appears to be at least a partial description of corneal rigidity. The ocular determinants of CH are unclear.