title: Ocular cyclotorsion during customized laser ablation.
abstract: OBJECTIVE
  To compare the measured difference and degree of cyclotorsion in eyes undergoing customized laser ablation between the time of wavefront measurement and laser refractive surgery.
  
  
  METHODS
  The degree of cyclotorsion was measured in 1019 consecutive eyes of 732 patients who underwent wavefront-guided corneal ablation for the treatment of myopia with or without astigmatism with the Alcon LADARVision excimer laser. Prior to obtaining the wavefront measurement, the horizontal axis of each eye was marked. Cyclotorsional alignment was measured on the supine patient prior to beginning the laser.
  
  
  RESULTS
  The predominant trend was for excyclotorsion. The total range of torsion in degrees was 0.5 degrees to 17.5 degrees (mean: 4.05 +/- 2.9 degrees). Cyclotorsion > 2 degrees occurred in 68% of all eyes. In the right eyes, 83% excyclotorted, 14% incyclotorted, and 3% displayed no torsion. In the left eyes, 62% excyclotorted, 34% incyclotorted, and 4% exhibited no torsion. In a subset of 112 patients undergoing simultaneous bilateral surgery, 46% displayed bilateral excyclotorsion and 1.7% displayed bilateral incyclotorsion.
  
  
  CONCLUSIONS
  In this study, the majority of eyes had a low to moderate amount of cyclotorsion observed with the change of orientation from seated to supine position. Excyclotorsion was the predominant pattern. Proper registration prior to wavefront-guided corneal ablation is essential for proper correction of astigmatism and higher order aberrations to achieve optimal visual outcomes.
authors.affiliation: Department of Ophthalmology, Kansas University Medical Center, USA.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Ciccio
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Durrie
authors.forename: Jason E
authors.initials: JE
authors.lastname: Stahl
authors.forename: Frank
authors.initials: F
authors.lastname: Schwendeman
mesh_terms: D003315:Cornea / Q000601:surgery*; D003941:Diagnostic Techniques, Ophthalmological; D005128:Eye Diseases / Q000209:etiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007432:Intraoperative Period; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011187:Posture; D012189:Retrospective Studies; D014102:Torsion Abnormality / Q000209:etiology