title: Reproducibility of ocular response analyzer measurements and their correlation with central corneal thickness.
abstract: BACKGROUND
  To evaluate the inter- and intraobserver variability of ocular response analyzer (ORA) measurements, namely corneal-compensated intraocular pressure (IOPcc), corneal resistance factor (CRF) and corneal hysteresis (CH).
  
  
  METHODS
  One randomly chosen eye of 46 healthy volunteers was included in this study. Three clinical observers performed three consecutive measurements using ORA, with an interval of 1-2 minutes between measurements. In all subjects, central corneal thickness (CCT) was measured. The inter- and intraobserver reproducibility for IOPcc, CRF and CH was assessed by ANOVA-based intraclass correlation coefficient (ICC) and coefficient of variation (CV).
  
  
  RESULTS
  The mean ICC for interobserver reproducibility was 0.94 for IOPcc, 0.90 for CRF, and 0.86 for CH. The corresponding CV values were 12.8%, 10.3%, and 13.6% respectively. The intraobserver ICC values for IOPcc were 0.86 for the first examiner, 0.84 for the second, and 0.89 for the third. CV was 11.7%, 11.9%, and 11.0% respectively. For CRF, the intraobserver ICC values were 0.69, 0.81, and 0.63, and corresponding CV values were 9.6%, 8.1, and 10.8%. The intraobserver ICC for CH was 0.66 for the first observer, 0.71 for the second, and 0.61 for the third examiner. The respective CV values were 12.7%, 11.8%, and 13.9%. There was a significant correlation between CCT and CRF (Rsq = 0.13, p = 0.02). The correlations of CCT with IOPcc and CH were not significant (p > 0.05).
  
  
  CONCLUSIONS
  The interobserver reproducibility of ORA measurements was almost perfect for IOPcc, CRF, and CH. The intraobserver short-term reproducibility was almost perfect for IOPcc and substantial for CRF and CH, for all observers. The significant correlation between CCT and CRF, and no association between IOPcc and CCT, are in agreement with previous studies. There was no significant correlation between CH and CCT in our study. This device might be useful in glaucoma diagnosis and management.
authors.affiliation: Department of Ophthalmology of the University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany. poslednik@gmx.net
authors.forename: Joanna
authors.initials: J
authors.lastname: Wasielica-Poslednik
authors.forename: Fatmire
authors.initials: F
authors.lastname: Berisha
authors.forename: Shakhsanam
authors.initials: S
authors.lastname: Aliyeva
authors.forename: Norbert
authors.initials: N
authors.lastname: Pfeiffer
authors.forename: Esther M
authors.initials: EM
authors.lastname: Hoffmann
mesh_terms: D003315:Cornea / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*; D014792:Visual Acuity / Q000502:physiology