[Ocular response analyzer: feasibility study and correlation w...

INTRODUCTION: To evaluate the accuracy of ocular response analyzer (ORA) parameters (corneal hysteresis (CH), corneal resistance factor (CRF), and ocular tension (IOPcc and IOPg)) and the correlation with corneal biometry measured with the Orbscan topographer. MATERIAL: and methods: The Ocular Response Analyzer is a new instrument that measures ocular rigidity/elasticity (CH and CRF) and intraocular pressure (IOPcc), which is assumed to be independent of corneal pachymetry. We compared the results of the ORA in 100 eyes with normal slit lamp examination, except ametropia, with the results from corneal measurements obtained with the Orbscan. RESULTS: A high correlation and a low difference between the right and left eyes show the accuracy of measurements (rS=0.84, p<0.001 and 8.52%). The mean CH and CRF were 10.25+/-1.6 mmHg (range, 6.5-14.4) and 10.25+/-1.85 mmHg (range, 4.9-14.2), respectively with a Gaussian distribution in normal eyes. The relationship between CH and CRF was significant with corneal pachymetry but not with IOPcc (corneal corrected). CH and CRF were related, although to a lesser extent, with corneal diameter and astigmatism power, but not to keratometry, sex, age, or spherical equivalent. CONCLUSION: The mean and the distribution of biomechanical factors are similar to the values found in the literature but the relationship to pachymetry seems to be stronger (pachymetry and corneal diameter) than what has been reported in previous publications. The new IOP corrected for the cornea is independent of pachymetry but is not significantly different from Goldmann IOP or IOP measured with a standard noncontact tonometer.