title: Risk assessment for ectasia after corneal refractive surgery.
abstract: OBJECTIVE
  To analyze the epidemiologic features of ectasia after excimer laser corneal refractive surgery, to identify risk factors for its development, and to devise a screening strategy to minimize its occurrence.
  
  
  METHODS
  Retrospective comparative and case-control study.
  
  
  METHODS
  All cases of ectasia after excimer laser corneal refractive surgery published in the English language with adequate information available through December 2005, unpublished cases seeking treatment at the authors' institution from 1998 through 2005, and a contemporaneous control group who underwent uneventful LASIK and experienced a normal postoperative course.
  
  
  METHODS
  Evaluation of preoperative characteristics, including patient age, gender, spherical equivalent refraction, pachymetry, and topographic patterns; perioperative characteristics, including type of surgery performed, flap thickness, ablation depth, and residual stromal bed (RSB) thickness; and postoperative characteristics including time to onset of ectasia.
  
  
  METHODS
  Development of postoperative corneal ectasia.
  
  
  RESULTS
  There were 171 ectasia cases, including 158 published cases and 13 unpublished cases evaluated at the authors' institution. Ectasia occurred after LASIK in 164 cases (95.9%) and after photorefractive keratectomy (PRK) in 7 cases (4.1%). Compared with controls, more ectasia cases had abnormal preoperative topographies (35.7% vs. 0%; P<1.0x10(-15)), were significantly younger (34.4 vs. 40.0 years; P<1.0x10(-7)), were more myopic (-8.53 vs. -5.09 diopters; P<1.0x10(-7)), had thinner corneas before surgery (521.0 vs. 546.5 microm; P<1.0x10(-7)), and had less RSB thickness (256.3 vs. 317.3 microm; P<1.0x10(-10)). Based on subgroup logistic regression analysis, abnormal topography was the most significant factor that discriminated cases from controls, followed by RSB thickness, age, and preoperative corneal thickness, in that order. A risk factor stratification scale was created, taking all recognized risk factors into account in a weighted fashion. This model had a specificity of 91% and a sensitivity of 96% in this series.
  
  
  CONCLUSIONS
  A quantitative method can be used to identify eyes at risk for developing ectasia after LASIK that, if validated, represents a significant improvement over current screening strategies.
authors.affiliation: Department of Ophthalmology, Emory University, Atlanta, Georgia, USA. Jrandle@emory.edu
authors.forename: J Bradley
authors.initials: JB
authors.lastname: Randleman
authors.forename: Maria
authors.initials: M
authors.lastname: Woodward
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lynn
authors.forename: R Doyle
authors.initials: RD
authors.lastname: Stulting
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003316:Corneal Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D019781:Corneal Topography; D004108:Dilatation, Pathologic / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D018903:Photorefractive Keratectomy; D011183:Postoperative Complications; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity