title: Rigid contact lens fitting relationships in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group.
abstract: OBJECTIVE
  Although the influence of flat-fitting contact lenses on corneal scarring in keratoconus is frequently debated, the current standard of care with regard to the apical fitting relationship in keratoconus remains undocumented.
  
  
  METHODS
  Patients were examined at baseline in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study (N = 1209). Patients wearing a rigid contact lens in one or both eyes (N = 808) had their habitual rigid contact lenses analyzed, and the fluorescein patterns and base curves were compared to the first definite apical clearance lens (FDACL). The FDACL is the flattest lens in the CLEK Study trial lens set that exhibits an apical clearance fluorescein pattern. For patients wearing a rigid contact lens in both eyes, one eye was selected randomly for analysis.
  
  
  RESULTS
  Twelve percent of the rigid contact lens-wearing eyes were wearing lenses fitted with apical clearance based upon the clinician's fluorescein pattern interpretation. The remainder (88%) was wearing lenses fitted with apical touch. For mild (steep keratometric reading <45 D) keratoconus corneas, the mean estimate of the base curve to cornea-fitting relationship was 1.18 D flat (SD +/- 1.84 D); moderate (steep keratometric reading: 45 to 52 D) corneas were fitted on average 2.38 D flat (SD +/- 2.56 D); and severe (steep keratometric reading > 52 D) corneas were fitted an average of 4.01 D flat (SD +/- 4.11 D).
  
  
  CONCLUSIONS
  Despite the potential risk for corneal scarring imposed by flat-fitting rigid contact lenses, most CLEK Study patients wear flat-fitting lenses. Overall, rigid lenses were fitted an average of 2.86 D (SD +/- 3.31 D) flatter than the FDACL.
authors.affiliation: Southern California College of Optometry, Fullerton, USA.
authors.forename: T B
authors.initials: TB
authors.lastname: Edrington
authors.forename: L B
authors.initials: LB
authors.lastname: Szczotka
authors.forename: J T
authors.initials: JT
authors.lastname: Barr
authors.forename: J F
authors.initials: JF
authors.lastname: Achtenberg
authors.forename: D S
authors.initials: DS
authors.lastname: Burger
authors.forename: A M
authors.initials: AM
authors.lastname: Janoff
authors.forename: H E
authors.initials: HE
authors.lastname: Olafsson
authors.forename: M W
authors.initials: MW
authors.lastname: Chun
authors.forename: J W
authors.initials: JW
authors.lastname: Boyle
authors.forename: M O
authors.initials: MO
authors.lastname: Gordon
authors.forename: K
authors.initials: K
authors.lastname: Zadnik
mesh_terms: D003261:Contact Lenses; D019781:Corneal Topography; D004867:Equipment Design; D006801:Humans; D007640:Keratoconus / Q000628:therapy*; D017755:Prosthesis Fitting / Q000379:methods*