title: Keratectasia after laser in situ keratomileusis (LASIK): evaluation of the calculated residual stromal bed thickness.
abstract: OBJECTIVE
  To report corneal histopathology associated with keratectasia after laser in situ keratomileusis (LASIK) and to evaluate the thickness of the calculated residual stromal bed in two cases and those in the literature.
  
  
  METHODS
  Interventional case reports.
  
  
  METHODS
  Three eyes of two patients developed keratectasia after LASIK. Corneal specimens after penetrating keratoplasty in one eye of each patient were studied histopathologically, and the residual stromal bed was directly measured. For comparison, residual stromal bed thicknesses were calculated from published cases of keratectasia.
  
  
  RESULTS
  Two eyes of a 26-year-old woman and one eye of a 22-year-old woman developed keratectasia after LASIK. Calculated residual stromal bed thicknesses were 210, 213, and 261 microm. Histologic sections revealed focal scarring in the flap plane. The cornea specimens measured 75 and 118 microm thinner than calculated values immediately after LASIK. Transmission electron microscopy of one case revealed an average lamellar thickness of 0.94 microm. In 28 (49%) of 57 previous cases of keratectasia, the calculated residual stromal bed thicknesses were greater than 250 microm.
  
  
  CONCLUSIONS
  Both the flap and the stromal bed of the cornea may thin after LASIK. A residual stromal bed thickness of 250 microm does not preclude the development of keratectasia after LASIK.
authors.affiliation: Jules Stein Eye Institute, Department of Ophthalmology, "David Geffen" School of Medicine at UCLA, Los Angeles, California 90095, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Ou
authors.forename: Edward L
authors.initials: EL
authors.lastname: Shaw
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Glasgow
mesh_terms: D000328:Adult; D003316:Corneal Diseases / Q000175:diagnosis / Q000209:etiology* / Q000601:surgery; D003319:Corneal Stroma / Q000473:pathology* / Q000601:surgery; D004108:Dilatation, Pathologic; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D015948:Keratoplasty, Penetrating; D013524:Surgical Flaps