title: Peripheral refraction in orthokeratology patients.
abstract: OBJECTIVE
  The purpose of this study is to measure refraction across the horizontal central visual field in orthokeratology patients before and during treatment.
  
  
  METHODS
  Refractions were measured out to 34 degrees eccentricity in both temporal and nasal visual fields using a free-space autorefractor (Shin-Nippon SRW5000) for the right eyes of four consecutively presenting myopic adult patients. Measurements were made before orthokeratology treatment and during the course of treatment (usually 1 week and 2 weeks into treatment). Refractions were converted into mean sphere (M), 90 degrees to 180 degrees astigmatism (J180), and 45 degrees to 135 degrees astigmatism (J45) components.
  
  
  RESULTS
  Before treatment, subjects had either a relatively constant mean sphere refraction across the field or a relative hypermetropia in the periphery as compared with the central refraction. As a result of treatment, myopia decreased but at reduced rate out into the periphery. Most patients had little change in mean sphere at 30 degrees to 34 degrees . In all patients, the refraction pattern altered little after the first week.
  
  
  CONCLUSIONS
  Orthokeratology can correct myopia over the central +/- 10 degrees of the visual field but produces only minor changes at field angles larger than 30 degrees . If converting relative peripheral hypermetropia to relative peripheral myopia is a good way of limiting the axial elongation that leads to myopia, orthokeratology is an excellent option for achieving this.
authors.affiliation: Faculty of Health Science, University of Manchester, Manchester, United Kingdom.
authors.forename: W Neil
authors.initials: WN
authors.lastname: Charman
authors.forename: John
authors.initials: J
authors.lastname: Mountford
authors.forename: David A
authors.initials: DA
authors.lastname: Atchison
authors.forename: Emma L
authors.initials: EL
authors.lastname: Markwell
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D003261:Contact Lenses; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D018450:Disease Progression; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009216:Myopia / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D012029:Refraction, Ocular / Q000502:physiology*; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology