title: Predictive factors of femtosecond laser flap thickness measured by online optical coherence pachymetry subtraction in sub-Bowman keratomileusis.
abstract: OBJECTIVE
  To evaluate possible factors responsible for the difference between predicted and measured parameters during 100 microm flap creation with a femtosecond laser (IntraLase FS30) using online optical coherence pachymetry (OCP).
  
  
  METHODS
  AugenVersorgungsZentrum, Weilheim, and the Technical University of Munich, Munich, Germany.
  
  
  METHODS
  In this nonrandomized prospective interventional case study, 287 eyes of 146 consecutive patients were monitored by online OCP before and after flap creation with the femtosecond laser. The laser-specific settings were held constant during the study to attempt a 100 microm flap in all eyes. A multiple linear regression model with backward variable selection procedure was applied to evaluate possible multivariable explanatory powers of several covariates. In addition, very thin and very thick flaps (ie, lower and upper quartiles of flap thickness distribution) were analyzed separately in a logistic regression model.
  
  
  RESULTS
  Central flap thickness measured with online OCP subtraction varied according to a Gaussian distribution from 57 to 138 microm, with a mean of 100.4 microm +/- 13.6 (SD). Regression analysis between predicted and measured flap thickness showed no predictive power of 11 variables including the keratometry value of the cornea, preoperative corneal thickness, and patient age.
  
  
  CONCLUSIONS
  The plano applanation interface of the IntraLase FS30 femtosecond laser produced ultrathin flaps for sub-Bowman keratomileusis that were independent of some preoperative and surgical factors known to affect outcomes with mechanical microkeratomes.
authors.affiliation: AugenVersorgungsZentrum, Weilheim, Germany. pfaeffl@msn.com
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Pfaeffl
authors.forename: Miriam
authors.initials: M
authors.lastname: Kunze
authors.forename: Ulrich
authors.initials: U
authors.lastname: Zenk
authors.forename: Matthias B
authors.initials: MB
authors.lastname: Pfaeffl
authors.forename: Tibor
authors.initials: T
authors.lastname: Schuster
authors.forename: Chris
authors.initials: C
authors.lastname: Lohmann
mesh_terms: D000293:Adolescent; D000328:Adult; D050541:Bowman Membrane / Q000601:surgery*; D003319:Corneal Stroma / Q000473:pathology*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007368:Interferometry / Q000379:methods; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008027:Light; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D009862:Online Systems; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D013524:Surgical Flaps / Q000473:pathology*; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult