Inter-eye Differences in the Clinical Assessment of Intraocular Pressure and Ocular Biomechanics

Clinicians and researchers will have evidence whether intereye differences confound clinical measurements of intraocular pressure or of ocular biomechanical parameters.The purpose of this study was to determine whether intraocular pressure and biomechanical parameters, as measured by the Ocular Response Analyzer (ORA) and by Cornea Visualization with Scheimpflug Technology (CorVis ST), are different between the first and second eye measured.Intraocular pressure and biomechanical parameters were collected from both eyes of healthy participants (N = 139). The ORA measured corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure, and corneal hysteresis. The CorVis ST measured biomechanically corrected intraocular pressure, stiffness parameter at first applanation, and stiffness parameter at highest concavity. For each measurement, a paired t test compared the value of the first eye measured against that of the second eye measured.For the ORA, Goldmann-correlated intraocular pressure was significantly higher ( P = .001) in the first eye (14.8 [3.45] mmHg) than in the second eye (14.3 [3.63] mmHg). For the CorVis ST, biomechanically corrected intraocular pressure was significantly higher ( P < .001) in the second eye (14.7 [2.14] mmHg) than in the first eye (14.3 [2.11] mmHg). Stiffness parameter at first applanation (intereye difference, 6.85 [9.54] mmHg/mm) was significantly ( P < .001) higher in the first eye than in the second eye. Stiffness parameter at highest concavity was significantly higher ( P = .01) in the second eye (14.3 [3.18] mmHg/mm) than in the first eye (14.0 [3.13] mmHg/mm).Although there were statistically significant intereye differences in intraocular pressure and in biomechanical parameters for both devices, the variations were small and thus unlikely to affect clinical outcomes.