title: Maximum permissible lateral decentration in aberration-sensing and wavefront-guided corneal ablation.
abstract: OBJECTIVE
  To investigate the lateral alignment accuracy needed in wavefront-guided refractive surgery to improve the ocular optics to a desired level in a percentage of normally aberrated eyes.
  
  
  METHODS
  Department of Ophthalmology, University of Zurich, Zurich, Switzerland.
  
  
  METHODS
  The effect of laterally misaligned ablations on the optical outcome was simulated using measured wavefront aberration patterns from 130 normal eyes. The calculations were done for 3.0 mm, 5.0 mm, and 7.0 mm pupils. The optical quality of the simulated correction was rated by means of the root-mean-square residual wavefront error.
  
  
  RESULTS
  To achieve the diffraction limit in 95% of the normal eyes with a 7.0 mm pupil, a lateral alignment accuracy of 0.07 mm or better was required. An accuracy of 0.2 mm was sufficient to reach the same goal with a 3.0 mm pupil.
  
  
  CONCLUSIONS
  Procedures must be developed to ensure that the ablation is within a tolerance range based on each eye's original optical error. Rough centration based on the surgeon's judgment might not be accurate enough to achieve significantly improved optical quality in a high percentage of treated eyes.
authors.affiliation: Department of Ophthalmology, University of Zurich, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Bueeler
authors.forename: Michael
authors.initials: M
authors.lastname: Mrochen
authors.forename: Theo
authors.initials: T
authors.lastname: Seiler
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D005133:Eye Movements; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009799:Ocular Physiological Phenomena; D010469:Perceptual Distortion; D018903:Photorefractive Keratectomy; D011680:Pupil / Q000502:physiology; D012029:Refraction, Ocular / Q000502:physiology; D012030:Refractive Errors / Q000503:physiopathology; D054140:Refractive Surgical Procedures