title: Visual performance after photorefractive keratectomy with a 6-mm ablation zone.
abstract: OBJECTIVE
  To prospectively examine the effect of photorefractive keratectomy with a 6-mm ablation zone on best-spectacle-corrected visual performance.
  
  
  METHODS
  A prospective study was conducted of 164 eyes of 164 patients with an average (+/-SD) of -4.02 +/- 1.74 diopters (range, -0.63 to -8.38 diopters spherical equivalent). Best-spectacle-corrected high-contrast and low-contrast visual acuity (18% Weber contrast) was measured with both natural and dilated pupils. Patients were tested preoperatively and at 3, 6, and 12 months after photorefractive keratectomy. Photorefractive keratectomy was performed with an argon fluoride excimer laser. Fifty-five eyes of 55 patients also underwent astigmatic keratotomy.
  
  
  RESULTS
  Twelve months after photorefractive keratectomy, best-spectacle-corrected high-contrast visual acuity with natural pupils showed no significant change from preoperative values; mean (+/-SD) change was 0.004 +/- 0.10 logMAR (t = 0.45, P = .65). Best-spectacle-corrected low-contrast visual acuity with natural pupils was significantly reduced compared to baseline; mean (+/-SD) change was 0.04 +/- 0.13 logMAR (t = 3.3, P = .001). The low-contrast loss was larger (1.5 lines) with dilated pupils; mean (+/-SD) change was 0.13 +/- 0.15 logMAR (t = 9.31, P < .001). Greater losses in dilated low-contrast visual acuity were associated with concurrent astigmatic ketatotomy (t = 2.28, P = .025) and corneal haze of grade 1 or greater (t = 2.71, P = .005).
  
  
  CONCLUSIONS
  Reductions in visual performance occur after photorefractive keratectomy with a 6-mm zone. These changes are greatest for low-contrast visual acuity with dilated pupils. Corneal haze and concurrent astigmatic keratotomy are associated with greater losses in low-contrast visual acuity. Best-spectacle-corrected low-contrast visual acuity is a sensitive measure for evaluating visual performance after refractive surgery.
authors.affiliation: College of Optometry, Ohio State University, Columbus, USA. DrMaloney@Maloneyvision.com
authors.forename: M A
authors.initials: MA
authors.lastname: Bullimore
authors.forename: M D
authors.initials: MD
authors.lastname: Olson
authors.forename: R K
authors.initials: RK
authors.lastname: Maloney
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D054018:Lasers, Excimer; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology*