title: Analysis of actual corneal flap thickness and confounding factors between first and second operated eyes.
abstract: OBJECTIVE
  To calculate the actual corneal flap thickness during laser in-situ keratomileusis.
  
  
  METHODS
  Fifty-four women and 26 men with refractive error were enrolled in the study. Flaps were created using a MK-2000 microkeratome (Nidek, Gamagori, Japan) with a 130-microm head. The comparisons between both operated eyes of a patient and the correlations between flap thickness and confounding factors were analyzed.
  
  
  RESULTS
  The average flap thicknesses were 134.0 + or - 16.5 and 112.3 + or - 14.4 microm in the first and second operated eye groups, respectively, and the data showed a significant difference between the two groups (P < .001). There were positive correlations between central corneal thickness and flap thickness (first group, P = .017; second group, P = .041).
  
  
  CONCLUSIONS
  The flap thicknesses of the first operated eye group were thicker than those of the second operated eye group and there was a positive correlation between the flap thickness and central corneal thickness. The coefficient of variation of the flap thickness was greater in the second group than in the first group.
authors.affiliation: Department of Ophthalmology, Buddhist Tzu Chi General Hospital and Institute of Medical Sciences, and the Department of Ophthalmology and Visual Science, Institute of Medicine, Tzu Chi University, No 707, Section 3, Chung Yang Road, Hualien, Taiwan.
authors.forename: Sheng-Yao
authors.initials: SY
authors.lastname: Hsu
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Chen
authors.forename: Chin-Pin
authors.initials: CP
authors.lastname: Chung
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D001835:Body Weight; D003319:Corneal Stroma / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D007839:Functional Laterality; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D008297:Male; D033401:Microscopy, Acoustic; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D012029:Refraction, Ocular; D013524:Surgical Flaps / Q000473:pathology*; D014792:Visual Acuity