title: PRK in patients with a keratoconic topography picture. The concept of a physiological 'displaced apex syndrome'.
abstract: OBJECTIVE
  Keratoconus is generally held to be an absolute contraindication for photorefractive keratectomy (PRK). Corneas with inferior steepening on corneal topography are widely thought to have subclinical keratoconus. We were not convinced that this is always the case, as there seems to be a group of patients with a stable inferior steepening pattern on topography who show no other characteristics of clinical keratoconus. We thus decided to offer PRK to some of these patients under strictly defined criteria.
  
  
  METHODS
  Four myopic patients with a topography pattern of inferior steepening were submitted to PRK. They were selected on the basis of being aged over 35, with a stable refraction, no slit-lamp signs of keratoconus, and a corrected vision of not less than 6/7 (0.9) with a spherical spectacle correction. They gave fully informed consent that this was an experimental procedure.
  
  
  RESULTS
  The refractive results at 6 months after operation were within the range one would expect for PRK on corneas with a regular 'bow-tie' topography and similar level of myopia. No unusual problems were encountered.
  
  
  CONCLUSIONS
  We feel that the corneal topography pattern of inferior steepening is not always a contraindication for PRK. The concept of a physiological 'displaced apex syndrome' is discussed and illustrated by corneal topography in different positions of gaze.
authors.affiliation: Optimax Laser Eye Clinic, Manchester.
authors.forename: S J
authors.initials: SJ
authors.lastname: Doyle
authors.forename: E
authors.initials: E
authors.lastname: Hynes
authors.forename: S
authors.initials: S
authors.lastname: Naroo
authors.forename: S
authors.initials: S
authors.lastname: Shah
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology*; D003316:Corneal Diseases / Q000150:complications / Q000175:diagnosis / Q000601:surgery*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007640:Keratoconus / Q000175:diagnosis; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000209:etiology; D018903:Photorefractive Keratectomy