title: Multipass versus single pass photorefractive keratectomy for high myopia using a scanning laser.
abstract: OBJECTIVE
  To study photorefractive keratectomy (PRK) for high myopia using the Nidek EC-5000 slit scanning laser and to compare a single pass versus a multipass ablation approach.
  
  
  METHODS
  We retrospectively studied 95 eyes (64 patients; range -10.00 to -27.00 D; mean -12.00 D) treated for high myopia using PRK with a single or multipass technique. Forty-two eyes were treated with the single pass technique and 53 eyes were treated with the multipass technique.
  
  
  RESULTS
  Twelve months after PRK, 79.4% (27 eyes) of the multipass group and 48.1% (13 eyes) of the single pass group were within +/-1.00 D of emmetropia; 32.4% (11 eyes) of multipass eyes and 29.6% (8 eyes) of single pass eyes were within +/-0.50 D of emmetropia. Uncorrected visual acuity of 20/40 or better was reached by 85.3% (29 eyes) and 20/20 or better was reached by 55.9% (19 eyes) in the multipass group at 12 months postoperatively. For the single pass group, 74.1% (20 eyes) achieved 20/40 uncorrected and 18.5% (5 eyes) achieved 20/20 uncorrected visual acuity. No multipass-treated eyes lost 2 lines of spectacle-corrected visual acuity at 6 or 12 months postoperatively. Mean regression between 1 to 12 months after PRK was 0.46 D for the multipass group and 1.45 D for the single pass group. Most of the regression occurred within the first 6 months after surgery in both techniques.
  
  
  CONCLUSIONS
  These PRK results showed that treating high myopia using the Nidek EC-5000 excimer laser combined with a multipass approach generated good refractive outcomes with no complications. Undercorrections with the single pass technique could be compensated for with new nomograms. The multipass technique resulted in less regression and better refractive outcomes.
authors.affiliation: Michel Pop Clinics, Montreal, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Pop
authors.forename: Y
authors.initials: Y
authors.lastname: Payette
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D054018:Lasers, Excimer; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000295:instrumentation* / Q000379:methods*; D012029:Refraction, Ocular; D012189:Retrospective Studies; D016896:Treatment Outcome; D014792:Visual Acuity