title: The impact of overnight wear on the risk of contact lens-associated ulcerative keratitis.
abstract: OBJECTIVE
  To assess the relative risk of contact lens-associated ulcerative keratitis by lens type and related lens-wearing behavior.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Forty practice-based case patients with contact lens-associated ulcerative keratitis and 180 control patients matched to the case patients' dispensing practitioner and date of contact lens prescription.
  
  
  RESULTS
  Compared with users of daily-wear soft lenses, users of disposable soft contact lenses had a 13.33-fold (95% confidence interval [CI], 5.35 to 33.20) excess risk of ulcerative keratitis. However, after adjusting for overnight wear, the excess risk associated with disposable contact lenses is reduced to 3.21 (95% CI, 1.22 to 14.36). Overall, overnight wear of contact lenses conferred an 8.25-fold excess risk (95% CI, 3.33 to 25.58) of ulcerative keratitis after controlling for lens type. No protective effect of standard compared with substandard lens hygiene was found. The risk of ulcerative keratitis attributable to overnight wear was estimated at 49% for users of daily-wear lenses and 74% for users of lenses approved for overnight wear.
  
  
  CONCLUSIONS
  Overnight wear of contact lenses is the overwhelming risk factor for ulcerative keratitis among contact lens users. We estimate that 49% to 74% of cases of contact lens-associated ulcerative keratitis could be prevented by eliminating overnight wear.
authors.affiliation: Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Md.
authors.forename: O D
authors.initials: OD
authors.lastname: Schein
authors.forename: P O
authors.initials: PO
authors.lastname: Buehler
authors.forename: J F
authors.initials: JF
authors.lastname: Stamler
authors.forename: D D
authors.initials: DD
authors.lastname: Verdier
authors.forename: J
authors.initials: J
authors.lastname: Katz
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D016001:Confidence Intervals; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects*; D003320:Corneal Ulcer / Q000209:etiology*; D004203:Disinfection / Q000379:methods; D004209:Disposable Equipment; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors