title: Biomechanical diagnosis of keratoconus: evaluation of the keratoconus match index and the keratoconus match probability.
abstract: OBJECTIVE
  To evaluate the diagnostic capacity of the Ocular Response Analyser's keratoconus match index (KMI) and keratoconus match probability (KMP) classification in a sample of keratoconus (KC) patients.
  
  
  METHODS
  Keratoconus match index and KMP from 114 KC eyes, randomly selected from 114 patients with bilateral keratoconus (KCG), were compared with the corresponding ones from 109 normal eyes (CG). Keratoconus match index's predictive accuracy was assessed by receiver operating curves (ROC). Keratoconus match probability level of agreement was evaluated at the different KC stages of the Amsler-Krumeich classification. Correlations were estimated with topographic keratoconus classification (TKC), keratoconus index (KI), index of surface variance (ISV), vertical asymmetry (IVA), height asymmetry (IHA), height decentration (IHD), minimal radius (Rmin), central corneal thickness (CCT), thinnest corneal thickness (TCT) mean keratometry (Km) and intraocular pressure (IOPg).
  
  
  RESULTS
  Mean KMI in KCG and CG was 0.20 ± 0.38 and 0.98 ± 0.25, respectively (p < 0.01). Significant KMI differences (p < 0.01) were detected in different KC groups [range: 0.62 ± 0.38 (KC 1), -0.62 ± 0.04 (KC 4)]. Significant correlation was detected between KC staging and KMI (r = -0.56, p < 0.0001). Keratoconus match probability identified 22.03% of the CG eyes as suspect. Moreover, KMP identified 7.01% and 23.68% of the KCG eyes as normal and suspect, respectively. Receiver operating curves analysis for KMI parameter indicated a predictive accuracy of 97.7% (cut-off point: 0.512, sensitivity: 91.18%, specificity: 94.34%).
  
  
  CONCLUSIONS
  Keratoconus match index seems to be a reliable index in keratoconus diagnosis and staging. Keratoconus match probability identifies a significant percentage of topographically defined KC and CG eyes as suspect. Diagnostic capacity of these novel indexes needs to be further explored.
authors.affiliation: Department of Ophthalmology, University Medical Center of Saarland UKS, Homburg/Saar, Germany. labiris@usa.net
authors.forename: Georgios
authors.initials: G
authors.lastname: Labiris
authors.forename: Zisis
authors.initials: Z
authors.lastname: Gatzioufas
authors.forename: Haris
authors.initials: H
authors.lastname: Sideroudi
authors.forename: Athanassios
authors.initials: A
authors.lastname: Giarmoukakis
authors.forename: Vassilios
authors.initials: V
authors.lastname: Kozobolis
authors.forename: Berthold
authors.initials: B
authors.lastname: Seitz
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000473:pathology / Q000503:physiopathology*; D019781:Corneal Topography / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis* / Q000503:physiopathology; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve