title: Comparison of 5-mm and 6-mm ablation zones in photorefractive keratectomy for myopia.
abstract: BACKGROUND
  Variation in ablation zone diameter may alter visual acuity and/or refractive effect in photorefractive keratectomy. Despite theoretical benefits of using a smaller diameter ablation zone, clinical studies suggest that a larger ablation zone may decrease problems associated with photorefractive keratectomy.
  
  
  METHODS
  The results of our initial 34 consecutive eyes treated with a 5-mm diameter ablation zone using a Summit Technology ExciMed UV200LA excimer laser were compared retrospectively to our initial 34 consecutive eyes treated with a 6-mm diameter ablation zone using a Summit OmniMed excimer laser. Eyes had a spherical equivalent refraction between -1.00 and -6.00 diopters (D) and astigmatism less than 1.00 D. Patients were followed for a minimum of 6 months.
  
  
  RESULTS
  Eyes treated with a 6-mm ablation zone had less hyperopia and a spherical equivalent refraction closer to emmetropia at 1, 2, and 3 months (P = 0.001). Eyes treated with a 6-mm ablation zone had better uncorrected visual acuity at 1 and 2 months (P = 0.001). Less subepithelial haze was noted at 2 months (P = 0.01) and 3 months (P = 0.002) in the 6-mm group. At 6 months postoperatively, 30 of 32 eyes (94%) treated with a 6-mm ablation zone had a spherical equivalent refraction within 0.50 D of emmetropia, and all 32 eyes (100%) were within 1.00 D of emmetropia; in the 5-mm ablation zone group, 28 of 34 eyes (80%) were within 0.50 D and 29 (85%) were within 1.00 D of emmetropia. Patients treated with a 6-mm ablation zone complained less of night halos and had fewer differences between night and day vision.
  
  
  CONCLUSIONS
  In this study of myopia of -1.00 D to -6.00 D, eyes treated with a 6-mm ablation zone achieve a more rapid visual recovery with less variation in refractive outcome and less adverse effects than those treated with a 5-mm ablation zone.
authors.affiliation: Sydney Refractive Surgery Centre, St. Leonards, NSW, Australia.
authors.forename: R S
authors.initials: RS
authors.lastname: Kalski
authors.forename: G
authors.initials: G
authors.lastname: Sutton
authors.forename: Y
authors.initials: Y
authors.lastname: Bin
authors.forename: M A
authors.initials: MA
authors.lastname: Lawless
authors.forename: C
authors.initials: C
authors.lastname: Rogers
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology; D003316:Corneal Diseases / Q000209:etiology / Q000473:pathology; D005069:Evaluation Studies as Topic; D005139:Eyeglasses; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000009:adverse effects / Q000379:methods*; D012029:Refraction, Ocular; D012189:Retrospective Studies; D014792:Visual Acuity