title: Analysis of waveform-derived ORA parameters in early forms of keratoconus and normal corneas.
abstract: OBJECTIVE
  To evaluate the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Depew, NY) performance in differentiating grades I and II keratoconus from normal corneas using 41 parameters individually and to assess the effect of analyzing all parameters together.
  
  
  METHODS
  This study compared the mean value of 41 ORA parameters in grades I and II keratoconus with healthy age-matched control eyes. Only eyes with a central corneal thickness between 500 and 600 μm were included. The area under the receiver operating characteristic curve was calculated for each of the 41 parameters independently and for all of the parameters together.
  
  
  RESULTS
  This study included 136 eyes with normal corneas and 68 eyes with grades I and II keratoconus. When analyzed individually, four ORA parameters (p1area, p1area1, p2area, and p2area1) had an area under the curve greater than 0.900 for discriminating between both groups. The p2area was the parameter that achieved the largest area under the curve individually (0.931). The area under the curve increased to 0.978 when analyzing all parameters together.
  
  
  CONCLUSIONS
  Alternative ORA parameters are better for differentiating grades I and II keratoconus from normal corneas than the four parameters originally available for ophthalmologists (corneal hysteresis, Goldmann-correlated intraocular pressure, corneal-compensated intraocular pressure, and corneal resistance factor). Although the ORA did not achieve 100% accuracy, the discrimination between these two groups was optimized by combining all parameters.
authors.affiliation: Brazilian Study Group of Artificial Intelligence, Maceio, Rio de Janeiro, Brazil. brunaventuramd@gmail.com
authors.forename: Bruna V
authors.initials: BV
authors.lastname: Ventura
authors.forename: Aydano P
authors.initials: AP
authors.lastname: Machado
authors.forename: Renato
authors.initials: R
authors.lastname: Ambrósio
authors.forename: Guilherme
authors.initials: G
authors.lastname: Ribeiro
authors.forename: Luana N
authors.initials: LN
authors.lastname: Araújo
authors.forename: Allan
authors.initials: A
authors.lastname: Luz
authors.forename: João Marcelo
authors.initials: JM
authors.lastname: Lyra
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000473:pathology* / Q000503:physiopathology; D019781:Corneal Topography / Q000379:methods; D057108:Corneal Wavefront Aberration / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012029:Refraction, Ocular; D013997:Time Factors; D055815:Young Adult