title: Multizone and transition zone photorefractive keratectomy for high myopia.
abstract: BACKGROUND
  Variations in ablation profile may alter the stability of refraction and cause adverse effects in photorefractive keratectomy. We compared the benefits of multizone and transition zone ablation in the treatment of high and extreme myopia.
  
  
  METHODS
  A scanning excimer laser system, Nidek EC-5000 was used with three-zone treatment and our results were compared retrospectively with results obtained in a group with a conventional ablation profile using a transition zone.
  
  
  RESULTS
  Six-month follow-up data were available for 65 eyes with a transition zone and 46 eyes with three-zone treatment. Postoperative mean (+/- SD) healing time was 2.98 days (+/- 0.12) and 3.02 days (+/- 0.15) and night vision disturbances were 16% and 11.5% respectively, (p > 0.05). Refractive regression was also similar in the two groups; uncorrected visual acuity of 20/40 or better was 90.77% and 89.14%. At 6 months postoperatively, the mean (+/- SD) corneal clarity score was 0.61 (+/- 0.29) in the transition zone group, and 0.51 (+/- 0.07) in the multizone group (p < 0.05).
  
  
  CONCLUSIONS
  No discernible differences between treatments were found in either epithelial healing or refractive outcome, such as regression, between the groups. Corneal haze was less in eyes treated with three-zone ablation.
authors.affiliation: Tianjin Eye Hospital, People's Republic of China.
authors.forename: K
authors.initials: K
authors.lastname: Zhao
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: T
authors.initials: T
authors.lastname: Zuo
authors.forename: H
authors.initials: H
authors.lastname: Wang
mesh_terms: D000328:Adult; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods; D011183:Postoperative Complications; D012189:Retrospective Studies; D016896:Treatment Outcome; D014792:Visual Acuity; D014945:Wound Healing