title: Corneal deformation signal waveform analysis in keratoconic versus post-femtosecond laser in situ keratomileusis eyes after statistical correction for potentially confounding factors.
abstract: OBJECTIVE
  To evaluate and compare corneal biomechanical waveform parameters between keratoconic and post-femtosecond laser in situ keratomileusis (LASIK).
  
  
  METHODS
  Jules Stein Eye Institute, University of California, Los Angeles, California, USA.
  
  
  METHODS
  Comparative case series.
  
  
  METHODS
  The Ocular Response Analyzer was used to obtain the corneal hysteresis (CH), corneal resistance factor (CRF), and 39 biomechanical waveform parameters in manifest keratoconic eyes and post-femtosecond LASIK eyes. Univariate tests were used to assess the difference in each parameter between the 2 groups of eyes. After controlling for central corneal thickness (CCT) and age, a logistic regression model was used to select the parameters most useful in distinguishing between the 2 groups.
  
  
  RESULTS
  After statistically controlling for the differences in CCT and age, 7 parameters were found to be the most useful in distinguishing between groups: aplhf (high frequency noise in the region between peaks [P1 and P2]; P<.0001), w2 (width of P2 at base; P=.001), dslop1 (down-slope of P1 of wave; P<.0001), aindex (degree of "non-monotonicity" of rising and falling edges of first peak of wave, P=.0007), uslope1 (upslope of the P1 of wave; P=.001), CH (P=.035), and P1area (area under P1 of wave; P=.006). The area under the receiver operating characteristic curve for the model using these parameters was 0.932.
  
  
  CONCLUSIONS
  Differences in multiple biomechanical waveform parameters between the keratoconus and post-LASIK groups suggests that waveform analysis may be useful to differentiate between healthy and diseased biomechanical conditions.
authors.affiliation: From Jules Stein Eye Institute, University of California, Los Angeles, California, USA.
authors.forename: Siamak
authors.initials: S
authors.lastname: Zarei-Ghanavati
authors.forename: Arturo
authors.initials: A
authors.lastname: Ramirez-Miranda
authors.forename: Fei
authors.initials: F
authors.lastname: Yu
authors.forename: D Rex
authors.initials: DR
authors.lastname: Hamilton
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001696:Biomechanical Phenomena / Q000502:physiology; D015986:Confounding Factors, Epidemiologic; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D057108:Corneal Wavefront Aberration / Q000503:physiopathology; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D012189:Retrospective Studies; D055815:Young Adult