title: Predictability and outcomes of photoastigmatic keratectomy using the Nidek EC-5000 excimer laser.
abstract: OBJECTIVE
  To evaluate the effect of astigmatic correction on the accuracy of the myopic and astigmatic correction in patients having photorefractive astigmatic keratectomy (PARK) and in those having photorefractive keratectomy (PRK).
  
  
  METHODS
  Specialist excimer laser refractive clinic.
  
  
  METHODS
  This prospective consecutive case series comprised 6097 eyes with a preoperative mean spherical equivalent (MSE) of -4.63 diopters (D) +/- 1.95 (SD) (range -0.75 to -13.00 D) and a mean cylinder of -1.13 +/- 0.73 D (range -0.50 to -6.00 D) having PARK with a Nidek EC-5000 excimer laser. Visual and refractive outcomes were assessed 12 months postoperatively and compared with those in 3004 eyes that had spherical PRK.
  
  
  RESULTS
  At 12 months, the MSE was -0.02 +/- 0.79 D and the mean cylinder was -0.49 +/- 0.47 D in the PARK group; the MSE was -0.07 +/- 0.66 D in the PRK group. An MSE within +/-0.05 D of emmetropia was achieved by 69.8% and within +/-1.00 D, by 87.9%. The uncorrected visual acuity (UCVA) was 20/20 or better in 42.6% and 20/40 or better in 91.2%. Statistical significance (P <.001, analysis of variance) was achieved for MSE, sphere, cylinder, haze, and visual acuity (best corrected [BCVA] and UCVA) based on the preoperative cylinder. The loss of BCVA varied from 1.1% to 5.8% depending on the degree of astigmatism treated. Accuracy varied with the attempted myopic correction and the attempted astigmatic correction.
  
  
  CONCLUSIONS
  Excimer laser PARK was an effective treatment for compound myopic astigmatism, but predictability decreased and complications increased as the attempted astigmatic correction increased.
authors.affiliation: Optimax Laser Eye Clinic, Manchester, England. sunilshah@doctors.org.uk
authors.forename: Sunil
authors.initials: S
authors.lastname: Shah
authors.forename: Anupam
authors.initials: A
authors.lastname: Chatterjee
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Smith
mesh_terms: D000328:Adult; D000368:Aged; D001251:Astigmatism / Q000601:surgery*; D003315:Cornea / Q000601:surgery*; D006801:Humans; D054018:Lasers, Excimer; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011183:Postoperative Complications; D011446:Prospective Studies; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D016896:Treatment Outcome; D014792:Visual Acuity