title: Diffractive smoothing of excimer laser ablation using a defocused beam.
abstract: OBJECTIVE
  To determine if excimer laser myopic ablation with a defocused laser image produces a smoother ablation profile than does focused laser light.
  
  
  METHODS
  An ArF excimer laser was used to ablate a 5.00-diopter myopic correction in test blocks using both a contracting and expanding iris aperture. Defocused ablation was performed using a contracting iris aperture by translating the target away from the laser source. A confocal laser scanning microscope was used to analyze the surface smoothness at 55x and 275x magnifications.
  
  
  RESULTS
  The confocal laser scanning micrographs revealed a series of sharply demarcated concentric ridges in the focused ablation, and less prominent, slightly wavy lines in the defocused ablation performed with a contracting aperture. The focused ablation with an expanding aperture also created concentric ridges toward the periphery, but with slightly smoother edges.
authors.affiliation: Doheny Eye Institute, University of Southern California School of Medicine, Los Angeles.
authors.forename: R R
authors.initials: RR
authors.lastname: Krueger
authors.forename: X W
authors.initials: XW
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Rudisill
authors.forename: S L
authors.initials: SL
authors.lastname: Trokel
authors.forename: P J
authors.initials: PJ
authors.lastname: McDonnell
mesh_terms: D007834:Lasers; D020366:Methylmethacrylate; D008768:Methylmethacrylates / Q000528:radiation effects*; D008853:Microscopy
chemical_list: D008768:Methylmethacrylates; D020366:Methylmethacrylate