title: Early biomechanical keratoconus pattern measured with an ocular response analyzer: curve analysis.
abstract: OBJECTIVE
  To estimate the ability of the Ocular Response Analyzer parameters to aid in the diagnosis of keratoconus in pre-laser in situ keratomileusis (LASIK) patients.
  
  
  METHODS
  Department of Ophthalmology, Bordeaux 2 University, Bordeaux Cedex, France.
  
  
  METHODS
  Evaluation of diagnostic test.
  
  
  METHODS
  This study compared eyes with mild stages of keratoconus (study group) with preoperative eyes that later had LASIK (control group). Corneas with a central thickness within 500 to 600 μm were targeted. The biomechanical measurements were acquired, and 12 parameters were analyzed after extraction from the signal data.
  
  
  RESULTS
  The study group comprised 103 eyes and the control group, 97 eyes. The mean corneal hysteresis (CH) was 9.2 mm Hg in study eyes and 10.1 mm Hg in control eyes and the mean corneal resistance factor (CRF), 8.9 mm Hg and 10.6 mm Hg, respectively. For a threshold of 9.6, CH had a sensitivity of 66% with a specificity of 67%. For a threshold of 9.7, the CRF had a sensitivity of 72% and a specificity of 77%. For 6 biomechanical parameters, the probability that a patient would present with keratoconus was 3 in 1000 if 1 parameter was over the chosen threshold.
  
  
  CONCLUSIONS
  If 1 of 6 parameters were over a chosen threshold, the probability that a patient would present with keratoconus would be almost 3 in 1000 instead of 9 in 1000 in a LASIK surgery cohort. Despite low sensitivity and specificity, some parameters provided by the corneal analyzer offered high negative likelihood ratios and deserve more study with bigger samples.
authors: Department of Ophthalmology, Bordeaux 2 University, Bordeaux Cedex, France. toubould@gmail.com
authors: David
authors: D
authors: Touboul
authors: Antoine
authors: A
authors: Bénard
authors: Ashraf M
authors: AM
authors: Mahmoud
authors: Anne
authors: A
authors: Gallois
authors: Joseph
authors: J
authors: Colin
authors: Cynthia J
authors: CJ
authors: Roberts
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D016022:Case-Control Studies; D002648:Child; D003315:Cornea / Q000503:physiopathology*; D003941:Diagnostic Techniques, Ophthalmological; D004548:Elasticity / Q000502:physiology*; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011300:Preoperative Care; D011336:Probability; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity