title: Eighteen-year follow-up of excimer laser photorefractive keratectomy.
abstract: OBJECTIVE
  To evaluate the long-term efficacy of photorefractive keratectomy (PRK).
  
  
  METHODS
  University Hospital, London, United Kingdom.
  
  
  METHODS
  Prospective case series.
  
  
  METHODS
  One eye of patients who had PRK 18 years previously was examined. All had myopic corrections with a 6.0 mm optical zone.
  
  
  RESULTS
  Forty-six patients were examined. The mean preoperative spherical equivalent (SE) refractive error was -4.86 diopters (D) (range -2.75 to -7.375 D). The mean programmed correction was -4.43 D (range -2.50 to -7.00 D). Between 1 year and 18 years, the mean change in SE was -0.31 D (P = .06) and a significant increase in variance occurred (P < .002). The mean change in SE was -0.54 D in patients younger than 40 years at the time of correction (P < .02) and -0.05 D in patients older than 40 years (P = .9). The mean SE change was -0.40 D in women (P < .04) and -0.08 D in men (P = .8). The efficacy index was 0.58. The safety index was 0.998. The corrected distance visual acuity (CDVA) improved significantly from 1 to 18 years (P < .01). Ninety-six percent of corneas were clear at 18 years, with a reduction in haze scores (P < .001). There was no evidence of ectasia.
  
  
  CONCLUSIONS
  A significant increase in myopic SE occurred between 1 year and 18 years after PRK in patients younger than 40 years and in women. Predictability decreased between 1 year and 18 years. The procedure was safe with no long-term complications. The CDVA and corneal transparency improved with time.
  
  
  BACKGROUND
  Dr. Marshall was a consultant to Summit Technology, Inc. No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the Keratoconus Research Institute (Shalchi, O'Brart, McDonald, Patel), Department of Ophthalmology, St. Thomas' Hospital, The London Vision Clinic (Archer), National Institute for Health Research Moorfields Biomedical Research Centre (Marshall), University College London, Institute of Ophthalmology, London, United Kingdom.
authors.forename: Zaid
authors.initials: Z
authors.lastname: Shalchi
authors.affiliation: From the Keratoconus Research Institute (Shalchi, O'Brart, McDonald, Patel), Department of Ophthalmology, St. Thomas' Hospital, The London Vision Clinic (Archer), National Institute for Health Research Moorfields Biomedical Research Centre (Marshall), University College London, Institute of Ophthalmology, London, United Kingdom. Electronic address: davidobrart@aol.com.
authors.forename: David P S
authors.initials: DP
authors.lastname: O'Brart
authors.affiliation: From the Keratoconus Research Institute (Shalchi, O'Brart, McDonald, Patel), Department of Ophthalmology, St. Thomas' Hospital, The London Vision Clinic (Archer), National Institute for Health Research Moorfields Biomedical Research Centre (Marshall), University College London, Institute of Ophthalmology, London, United Kingdom.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: McDonald
authors.affiliation: From the Keratoconus Research Institute (Shalchi, O'Brart, McDonald, Patel), Department of Ophthalmology, St. Thomas' Hospital, The London Vision Clinic (Archer), National Institute for Health Research Moorfields Biomedical Research Centre (Marshall), University College London, Institute of Ophthalmology, London, United Kingdom.
authors.forename: Parul
authors.initials: P
authors.lastname: Patel
authors.affiliation: From the Keratoconus Research Institute (Shalchi, O'Brart, McDonald, Patel), Department of Ophthalmology, St. Thomas' Hospital, The London Vision Clinic (Archer), National Institute for Health Research Moorfields Biomedical Research Centre (Marshall), University College London, Institute of Ophthalmology, London, United Kingdom.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Archer
authors.affiliation: From the Keratoconus Research Institute (Shalchi, O'Brart, McDonald, Patel), Department of Ophthalmology, St. Thomas' Hospital, The London Vision Clinic (Archer), National Institute for Health Research Moorfields Biomedical Research Centre (Marshall), University College London, Institute of Ophthalmology, London, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Marshall
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019781:Corneal Topography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult