title: [An analysis about the safe range of thickness of the residual corneal stroma bed after LASIK].
abstract: OBJECTIVE
  To ascertain the safe range of thickness of the residual corneal stroma bed and the length of stable time after LASIK operation.
  
  
  METHODS
  Two hundred and twenty seven eyes were randomly selected from cases treated with LASIK in 2000. The posterior curvature of cornea was measured by Obscan II preoperatively and 1, 2, 3, 6 months, 1 year and 2 year postoperatively. These data were compared and analyzed.
  
  
  RESULTS
  Ectasia of central corneal posterior surface was detected at different degrees in all cases at the early postoperative period after LASIK. Ectasia was more prominent in eyes with thinner corneal stroma bed (< 300 microm). In eyes with thicker corneal stroma, ectasia remained stable or reverting obviously during the first year. The posterior curvature of cornea had no significant difference between 1 year and 2 year after operation in all cases.
  
  
  CONCLUSIONS
  Ectasia of corneal posterior surface presents in the early postoperative period after LASIK. It is safer to reserve more than 300 microm of the corneal stroma bed. The posterior curvature of cornea of all cases remains stable after one year postoperatively.
authors.affiliation: Ophthalmic Center, the Second Affiliated Hospital, Chongqing University of Medical Sciences, Chongqing 400010, China. cqkryk@hotmail.com
authors.forename: Zhi-Yu
authors.initials: ZY
authors.lastname: Du
authors.forename: Ning-Ling
authors.initials: NL
authors.lastname: Wu
authors.forename: Da-Yong
authors.initials: DY
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Guo
authors.forename: Qing
authors.initials: Q
authors.lastname: Zheng
authors.forename: Pi-Song
authors.initials: PS
authors.lastname: Yan
mesh_terms: D000293:Adolescent; D000328:Adult; D003319:Corneal Stroma / Q000473:pathology*; D019781:Corneal Topography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*