title: Treatment of previous decentered excimer laser ablation with combined myopic and hyperopic ablations.
abstract: OBJECTIVE
  Decentration of the ablation zone is an occasional complication of excimer laser refractive surgery. We describe a technique to recenter the ablation zone without changing the refractive status obtained by the first surgery.
  
  
  METHODS
  Sixteen eyes of 14 patients had moderate or marked ablation decentration after previous excimer laser surgery for myopia, but with only minor residual refractive error. Five eyes had spectacle-corrected visual acuity loss and all these patients reported various symptoms such as halos, ghost images, or night driving difficulties. To recenter the ablation zone without changing the refraction, a combination myopic and hyperopic treatment was used. The hyperopic treatment was decentered toward the initial decentered myopic ablation. A myopia ablation of near equal dioptric value was then added, but decentered in the opposite direction. The Bausch & Lomb Technolas Keracor 217 laser was used.
  
  
  RESULTS
  After the first retreatment, the centration of the ablation zone was improved in 15 of the 16 eyes. All eyes with initial spectacle-corrected visual acuity loss recovered lines of visual acuity. Subjective decrease of symptoms was described as follows: nil in one eye, mild in one eye, moderate in four eyes, and marked in ten eyes. A second retreatment was needed in five eyes: in two to improve centration and in three to correct residual ametropia. The only complication (one eye) was induced decentration 180 degrees away from the initial decentration with a 1-line spectacle-corrected visual acuity loss, and additional retreatment was required.
  
  
  CONCLUSIONS
  A combination of decentered myopic and hyperopic ablation of an equivalent dioptric magnitude, each decentered 180 degrees apart, was a useful method to correct previous excimer laser treatment decentration, with minimal alteration of refractive status that was obtained by the initial surgery.
authors.affiliation: Centre Hospitalier de l'Université Laval, Quebec City, Canada. gilleslafond@videotron.ca
authors.forename: Gilles
authors.initials: G
authors.lastname: Lafond
authors.forename: Sylviane
authors.initials: S
authors.lastname: Bonnet
authors.forename: Leon
authors.initials: L
authors.lastname: Solomon
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology / Q000601:surgery*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000209:etiology / Q000601:surgery*; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects / Q000379:methods*; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000209:etiology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000009:adverse effects / Q000379:methods*; D011183:Postoperative Complications; D012029:Refraction, Ocular; D012086:Reoperation; D016896:Treatment Outcome; D014792:Visual Acuity