title: Manual limbal markings versus iris-registration software for correction of myopic astigmatism by laser in situ keratomileusis.
abstract: OBJECTIVE
  To compare the efficacy and safety of manual limbal markings and wavefront-guided treatment with iris-registration software in laser in situ keratomileusis (LASIK) for myopic astigmatism.
  
  
  METHODS
  National Taiwan University Hospital, Taipei, Taiwan.
  
  
  METHODS
  Eyes with myopic astigmatism had LASIK with a Technolas 217z laser. Eyes in the limbal-marking group had conventional LASIK (PlanoScan or Zyoptix tissue-saving algorithm) with manual cyclotorsional-error adjustments according to 2 limbal marks. Eyes in the iris-registration group had wavefront-guided ablation (Zyoptix) in which cyclotorsional errors were automatically detected and adjusted. Refraction, corneal topography, and visual acuity data were compared between groups. Vector analysis was by the Alpins method.
  
  
  RESULTS
  The mean preoperative spherical equivalent (SE) was -6.64 diopters (D) +/- 1.99 (SD) in the limbal-marking group and -6.72 +/- 1.86 D in the iris-registration group (P = .92). At 6 months, the mean SE was -0.42 +/- 0.63 D and -0.47 +/- 0.62 D, respectively (P = .08). There was no statistically significant difference between groups in the astigmatism correction, success, or flattening index values using 6-month postoperative refractive data. The angle of error was within +/-10 degrees in 73% of eyes in the limbal-marking group and 75% of eyes in the iris-registration group.
  
  
  CONCLUSIONS
  Manual limbal markings and iris-registration software were equally effective and safe in LASIK for myopic astigmatism, showing that checking cyclotorsion by manual limbal markings is a safe alternative when automated systems are not available.
authors.affiliation: Department of Ophthalmology, Buddhist Tzu Chi General Hospital Taipei Branch and National Taiwan University Hospital, Medical College, Taipei, Taiwan.
authors.forename: Elizabeth P
authors.initials: EP
authors.lastname: Shen
authors.forename: Wei-Li
authors.initials: WL
authors.lastname: Chen
authors.forename: Fung-Rong
authors.initials: FR
authors.lastname: Hu
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D016850:Limbus Corneae / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D012984:Software; D014102:Torsion Abnormality / Q000517:prevention & control; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult