title: Results of excimer laser retreatment of residual myopia after previous photorefractive keratectomy.
abstract: BACKGROUND
  Nine percent to 30% of all patients who undergo a single excimer laser photorefractive keratectomy (PRK) do not achieve an unaided visual acuity of 20/ 40 or better and may require optical correction to obtain adequate vision.
  
  
  METHODS
  The authors performed a retrospective analysis of the records of 164 patients who had undergone retreatment with the excimer laser for residual myopia after a previous PRK. Mean follow-up was 35.5 +/- 15.2 weeks (range, 26-104 weeks).
  
  
  RESULTS
  The mean spherical equivalent (MSE) before retreatment was -2.59 +/- 1.36 diopter (D) (range, -0.50 to -7.75 D). The final MSE after reablation was -0.52 +/- 1.36 D (range, 2.50 to -5.50). Of the 164 patients, 107 (65.2%) obtained a final refraction within 1.00 D of emmetropia and 111 (67.3%) achieved an unaided visual acuity of 20/40 or better. Only 10 patients (6.1%) lost more than one Snellen line of best-corrected visual acuity. The final MSE result for the subgroup of patients who had a pre-retreatment myopia of between -0.50 and -1.90 D (-0.31 +/- 1.09 D) was significantly closer to emmetropia than that of the subgroup with a residual myopia of -4.00 to -7.75 D (-1.62 +/- 1.94 D).
  
  
  CONCLUSIONS
  Excimer laser retreatment may provide a relatively safe and predictable method of correcting residual myopia after an earlier PRK with a 25% extra correction recommended for residual myopia.
authors.affiliation: Optimax Laser Eye Clinics, Manchester, England.
authors.forename: A
authors.initials: A
authors.lastname: Chatterjee
authors.forename: S
authors.initials: S
authors.lastname: Shah
authors.forename: D A
authors.initials: DA
authors.lastname: Bessant
authors.forename: S J
authors.initials: SJ
authors.lastname: Doyle
mesh_terms: D000328:Adult; D006801:Humans; D053685:Laser Therapy; D054018:Lasers, Excimer; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy; D011184:Postoperative Period; D012029:Refraction, Ocular; D012086:Reoperation; D012189:Retrospective Studies; D016896:Treatment Outcome; D014792:Visual Acuity