title: A clinical description of Ocular Response Analyzer measurements.
abstract: OBJECTIVE
  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.
authors.affiliation: School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia. wm.lau@unsw.edu.au
authors.forename: William
authors.initials: W
authors.lastname: Lau
authors.forename: David
authors.initials: D
authors.lastname: Pye
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000033:anatomy & histology* / Q000502:physiology; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D012016:Reference Values; D014065:Tonometry, Ocular / Q000295:instrumentation*; D055815:Young Adult