title: Clinical analysis of excimer laser photorefractive keratectomy using a multiple zone technique for severe myopia.
abstract: OBJECTIVE
  In an investigational procedure, excimer laser photorefractive keratectomy for severe myopia was performed at three clinical trial centers to determine the effectiveness of the multiple zone technique.
  
  
  METHODS
  A VisX Model Twenty/Twenty excimer laser (VisX, Santa Clara, California) was used to perform photorefractive keratectomy on 14 severely myopic eyes (-10.37 to -24.5 diopters) of 12 patients by using a multiple zone technique. Postoperative follow-up ranged from six months to two years; retreatments were performed on four patients, with a follow-up of at least nine months.
  
  
  RESULTS
  At six months postoperatively, before retreatment, three of the 14 eyes were within 2 diopters and seven of the 14 eyes were within 4 diopters of attempted correction. Regression of effect to more severe myopia was worse in five eyes treated with nitrogen gas blowing. Retreatments also demonstrated considerable myopic regression. Three patients had loss of two or more lines of best-corrected visual acuity, and these patients also had moderate or severe levels of haze.
  
  
  CONCLUSIONS
  Excimer laser photorefractive keratectomy for severe myopia using a multiple zone technique is associated with considerable regression, haze, and loss of best-corrected visual actuity, especially when performed in association with nitrogen gas blowing.
authors.affiliation: Doheny Eye Institute, Los Angeles, California.
authors.forename: R R
authors.initials: RR
authors.lastname: Krueger
authors.forename: J H
authors.initials: JH
authors.lastname: Talamo
authors.forename: M B
authors.initials: MB
authors.lastname: McDonald
authors.forename: R J
authors.initials: RJ
authors.lastname: Varnell
authors.forename: M D
authors.initials: MD
authors.lastname: Wagoner
authors.forename: P J
authors.initials: PJ
authors.lastname: McDonnell
mesh_terms: D000328:Adult; D003315:Cornea / Q000502:physiology / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D053685:Laser Therapy / Q000379:methods*; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011183:Postoperative Complications; D012029:Refraction, Ocular; D012086:Reoperation; D016896:Treatment Outcome; D014792:Visual Acuity