title: A summary of the findings from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. CLEK Study Group.
abstract: BACKGROUND
  This summary of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study includes the study design and results to date.
  
  
  METHODS
  The CLEK Study is a longitudinal, observational study of 1,209 patients with keratoconus. The study's main outcome measures are corneal scarring, visual acuity, corneal curvature, and quality of life.
  
  
  RESULTS
  These patients' mean age at baseline was 39.3 +/- 10.9 years, and they had moderate to severe keratoconus. Ninety-five percent of the patients had steep keratometric readings of at least 45 D, and 78% had best-corrected visual acuity of 20/40 or better in both eyes. Sixty-five percent of the patients wore rigid gas-permeable contact lenses in both eyes, and most of those (73%) reported that their lenses were comfortable. Most rigid gas-permeable contact lens wearers were fitted with apical touch (88%). Fifty-three percent had corneal scarring in one or both eyes, and corneal scarring was associated with corneal staining, contact lens wear, age, the presence of a Fleischer's ring, and a steeper cornea. Corneal scarring was associated with decreased high- and low-contrast visual acuity.
  
  
  CONCLUSIONS
  These results characterize keratoconus patients as rigid gas-permeable contact lens wearers with moderately steep corneas. Corneal scarring is associated with decreased vision in keratoconus.
authors.affiliation: University Hospitals of Cleveland and Case Western Reserve University, Department of Ophthalmology, Ohio, USA.
authors.forename: L B
authors.initials: LB
authors.lastname: Szczotka
authors.forename: J T
authors.initials: JT
authors.lastname: Barr
authors.forename: K
authors.initials: K
authors.lastname: Zadnik
mesh_terms: D000328:Adult; D003261:Contact Lenses; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D011446:Prospective Studies; D011788:Quality of Life; D015203:Reproducibility of Results; D014792:Visual Acuity / Q000502:physiology*