title: Characteristics of corneal ectasia after LASIK for myopia.
abstract: OBJECTIVE
  There are numerous reports of corneal ectasia after laser in situ keratomileusis (LASIK) for myopia without a consistent definition of this condition or a definitive etiology. We conducted a retrospective analysis of published case reports to describe common characteristics of this postoperative event and compared them with findings from a group of successful LASIK patients.
  
  
  METHODS
  A MEDLINE search for "LASIK" and "ectasia" yielded 21 relevant articles published before May 2003 (n = 86 eyes, 59 patients). A comparison group (n = 103 eyes, 63 patients) was selected from a clinic-based sample of successful LASIK patients with 12 months of follow-up after treatment. Descriptive statistics are reported as median and interquartile range. Comparisons were performed using the Wilcoxon rank sum, Wilcoxon signed rank, and chi-square tests.
  
  
  RESULTS
  Time to diagnosis of ectasia after LASIK was 13 months (6 to 20 months). Residual myopia in the ectasia group was -3.69 D (-6.00 to -2.13 D) and was significantly greater than the comparison group, -0.38 D (-0.75 to 0.00 D), P < 0.001. After surgery, eyes with ectasia had increased corneal toricity 2.87 D (2.00 to 4.9 D) with increased oblique astigmatism 1.3 D (0.23 to 2.89 D) relative to eyes in the comparison group 0.00 D (0.00 to 0.08 D), and a loss of 2 lines (-0.5 to -6 lines) of best spectacle-corrected visual acuity (all P < 0.001). Thirty-five percent of reported cases resulted in subsequent corneal transplantation.
  
  
  CONCLUSIONS
  Preoperative characteristics of corneal ectasia include worse visual acuity, less corneal thickness, greater residual myopia, and greater corneal toricity than nonectatic eyes. Treatment factors associated with corneal ectasia after LASIK are greater stromal ablation and less residual stromal bed thickness. Postoperative characteristics of corneal ectasia are myopic refractive error with increased astigmatism, worse spectacle-corrected visual acuity, increased corneal toricity with topographic abnormality, and progressive corneal thinning.
authors.affiliation: College of Optometry, Ohio State University, Columbus, 43210-1240, USA. twa.1@osu.edu
authors.forename: Michael D
authors.initials: MD
authors.lastname: Twa
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Nichols
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Joslin
authors.forename: Pete S
authors.initials: PS
authors.lastname: Kollbaum
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Edrington
authors.forename: Mark A
authors.initials: MA
authors.lastname: Bullimore
authors.forename: G Lynn
authors.initials: GL
authors.lastname: Mitchell
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Cruickshanks
authors.forename: David J
authors.initials: DJ
authors.lastname: Schanzlin
mesh_terms: D000328:Adult; D001837:Body Weights and Measures; D003315:Cornea / Q000473:pathology*; D004108:Dilatation, Pathologic / Q000145:classification / Q000209:etiology; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D011183:Postoperative Complications; D012189:Retrospective Studies; D013997:Time Factors; D014792:Visual Acuity