title: Technical improvements in photorefractive keratectomy for correction of high myopia.
abstract: OBJECTIVE
  To evaluate the effects of hardware and software improvements in photorefractive keratectomy (PRK) for the treatment of highly myopic eyes.
  
  
  METHODS
  A retrospective study was carried out in 554 patients (582 eyes) with myopia between -7.00 and -17.00 D (mean -11.20 +/- 3.60 D) who had undergone PRK using the Aesculap Meditec laser. Group 1 with a 5-mm-diameter single ablation zone; Group 2 with a 5-mm-diameter single zone surrounded by a 2-mm tapered transitional zone; Group 3 and Group 4, same as Group 2 but with the laser upgraded with a smoke aspiration control system (Group 3), and with a computer-controlled fluence (Group 4).
  
  
  RESULTS
  In Group 1 at 2 years after PRK (50 eyes), 10 eyes (20%) were within +/-1.00 D of attempted correction and 13 eyes (26%) were within +/-2.00 D. In Group 2 at 2 years (118 eyes), 42 eyes (36%) were within +/-1.00 D of attempted correction and 65 eyes (55%) were within +/-2.00 D. In Group 3 at 2 years (43 eyes), 18 eyes (42%) were within +/-1.00 D of attempted correction and 28 eyes (65%) were within +/-2.00 D. In Group 4 at 2 years (47 eyes), 25 eyes (53%) were within +/-1.00 D of attempted correction and 29 eyes (62%) were within +/-2.00 D.
  
  
  CONCLUSIONS
  Software and hardware improvements facilitated PRK correction of high myopia with reasonable predictability, especially if a tapered transition zone was used. At 12 and 24-month follow-up, only the use of a tapered transition zone was associated with a statistically significant improvement in predictability.
authors.affiliation: Eye Department, University of Naples Federico II, Naples, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cennamo
authors.forename: Nicola
authors.initials: N
authors.lastname: Rosa
authors.forename: Maria Angelica
authors.initials: MA
authors.lastname: Breve
authors.forename: Maria
authors.initials: M
authors.lastname: di Grazia
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000601:surgery*; D006801:Humans; D054018:Lasers, Excimer; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000295:instrumentation / Q000379:methods*; D012189:Retrospective Studies; D012985:Software Design; D016896:Treatment Outcome; D014792:Visual Acuity