title: Excimer laser photorefractive keratectomy for extreme myopia.
abstract: OBJECTIVE
  To determine the efficacy, predictability, and safety of excimer laser photorefractive keratectomy (PRK) in treating very high myopia.
  
  
  METHODS
  Laser Vision Harley Street, London, England.
  
  
  METHODS
  Eighty-eight patients whose spherical errors ranged from -6.00 to -20.00 diopters (D) had PRK with the VISX 20/20B excimer laser and a multizone ablation technique. The patients were divided into two groups of 44: those with errors up to -10.00 D and those with errors above -10.25 D. Visual acuity, manifest refraction, corneal haze, and topography were examined 1 week and 1, 2, 3, 6, and 12 months postoperatively.
  
  
  RESULTS
  Minimum follow-up was 1 year. Predictability of results was greater in Group 1 than in Group 2 patients: 90.0% were within 1.00 D of intended correction and 70.0% were within 2.00 D, respectively. The average for both groups was 85.0% within 2.00 D and 63.6% within 1.00 D of intended correction. No serious complications or overcorrections were seen in either group. Preoperative astigmatism ranged from 1.50 to 5.50 D. Postoperatively, 82.0% of patients had no residual astigmatism; in the other 18.0%, it ranged from 0.50 to 2.50 D (83.0% had 1.00 D or less). Results with the multizone technique were more successful than those reported with the single- or dual-zone ablation techniques.
  
  
  CONCLUSIONS
  High myopia was treated with reasonable success using the VISX 20/20B excimer laser system and a multizone technique. Comparable studies using single- and dual-zone approaches appear to have less successful outcomes.
authors.forename: D K
authors.initials: DK
authors.lastname: Williams
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D003318:Corneal Opacity / Q000209:etiology / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000009:adverse effects; D011183:Postoperative Complications; D012029:Refraction, Ocular / Q000502:physiology; D012449:Safety; D014792:Visual Acuity / Q000502:physiology