title: Measuring corneal hysteresis: threshold estimation of the waveform score from the Ocular Response Analyzer.
abstract: BACKGROUND
  The aim of this study was to determine a threshold waveform score (WS) for the best score value (BSV) in the Ocular Response Analyzer (ORA).
  
  
  METHODS
  Retrospective study. One hundred and thirty-three healthy adults were recruited. Measurements were done with the ORA 2.04.
  
  
  RESULTS
  Two hundred and sixty-six eyes were analyzed. Mean age was 56.49 ± 15.97 years. The mean waveform score of the BSV was 7.39 ± 1.32. The waveform scores ranged from 2.8 to 9.7. Kolmogorov-Smirnov test for normality was significant (p ≤ 0.0001).                 Linear regression showed a significant positive correlation between IOPg (measured with the ORA) and IOP measured with Goldmann applanation tonometry (p ≤ 0.0001), as well as significant negative correlation between the difference IOPg-IOP Goldmann and waveform score of the BSV values. Threshold estimation considering 95 % confidence interval was 7.23. Meanwhile, threshold estimation considering the difference IOPg-IOP Goldmann, for 3 mmHg, was 6.7.
  
  
  CONCLUSIONS
  When using the ORA device, we recommend that clinicians try to obtain several waveform score measurements of 7 or above. Waveform scores lower than 7 may render less reliable results.
authors.affiliation: Glaucoma Department, Karolinska Institutet, St. Erik Eye Hospital, Polhemsgatan 50, SE-112 82, Stockholm, Sweden. marcelo.ayala@sankterik.se
authors.forename: Marcelo
authors.initials: M
authors.lastname: Ayala
authors.forename: Enping
authors.initials: E
authors.lastname: Chen
mesh_terms: D003315:Cornea / Q000502:physiology*; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012684:Sensory Thresholds / Q000502:physiology; D013223:Statistics as Topic; D014065:Tonometry, Ocular / Q000295:instrumentation