title: Risk factors for corneal ectasia after LASIK.
abstract: OBJECTIVE
  To establish a grading system that helps identify high-risk individuals who may experience corneal ectasia after LASIK.
  
  
  METHODS
  Retrospective, comparative, interventional case series.
  
  
  METHODS
  One hundred forty-eight consecutive patients (148 eyes) were included in this study. Thirty-seven patients who underwent LASIK at other refractive centers experienced corneal ectasia in 1 eye after LASIK. One hundred eleven eyes of 111 patients who underwent successful LASIK during the same period were age and gender matched and served as controls.
  
  
  METHODS
  All patients underwent preoperative and postoperative topographic analysis of the cornea. The follow-up period in both groups of patients ranged from 2 to 5 years, with a mean follow-up of 3.6 years. All patients underwent LASIK for myopia (spherical equivalent, -4.00 to -8.00 diopters).
  
  
  METHODS
  Corneal keratometry, oblique cylinder, pachymetry, posterior surface elevation, difference between the inferior and superior corneal diopteric power, and posterior best sphere fit (BSF) over anterior BSF were given a grade of 1 to 3 each. An ectasia grading system was established, and the cumulative risk score was assessed.
  
  
  RESULTS
  Patients who had a grade of 7 or less showed no evidence of corneal ectasia, whereas 16 (59%) of 27 patients who had a grade of 8 to 12 had corneal ectasia. Twenty-one (100%) of 21 patients with a grade of more than 12 had corneal ectasia after LASIK (P<0.0001).
  
  
  CONCLUSIONS
  A risk score may help in the prediction of patients who are at risk of experiencing corneal ectasia after LASIK. A prospective clinical study is needed to assess the validity of these risk factors.
authors.affiliation: The Eye Center and The Eye Foundation for Research in Ophthalmology, Riyadh, Saudi Arabia.
authors.forename: Khalid F
authors.initials: KF
authors.lastname: Tabbara
authors.forename: Amgad A
authors.initials: AA
authors.lastname: Kotb
mesh_terms: D003315:Cornea / Q000473:pathology*; D003316:Corneal Diseases / Q000145:classification / Q000209:etiology*; D019781:Corneal Topography; D004108:Dilatation, Pathologic / Q000145:classification / Q000209:etiology; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D011183:Postoperative Complications; D012189:Retrospective Studies; D012307:Risk Factors; D014792:Visual Acuity