title: Excimer ablation design and elliptical transition zones.
abstract: OBJECTIVE
  To describe the rationale behind elliptical and other transition designs used with the excimer laser.
  
  
  METHODS
  Casey Eye Institute, Oregon Health Sciences University, Portland, Oregon, USA.
  
  
  METHODS
  Ablation zone designs were analyzed for the number of transition points for myopia and hyperopia. The advantages and disadvantages of elliptical transition zones are demonstrated graphically, with an emphasis on smooth ablation zone design to maximize the optics and biologic tolerance by the eye.
  
  
  RESULTS
  The use of an individualized elliptical transition maximizes a circular effective optical zone and can enhance the smoothness of the transition zone while minimizing excessive tissue removal.
  
  
  CONCLUSIONS
  Elliptical transition zones may improve the optics and biologic tolerance of excimer laser treatments.
authors.affiliation: Casey Eye Institute, Oregon Health Sciences University, Portland 97201-4197, USA.
authors.forename: S
authors.initials: S
authors.lastname: MacRae
mesh_terms: D003315:Cornea / Q000601:surgery*; D006801:Humans; D006956:Hyperopia / Q000601:surgery*; D054018:Lasers, Excimer; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*