title: Comparison of ablation centration in initial and retreatment active eye-tracker-assisted laser in situ keratomileusis and the effect on visual outcome.
abstract: OBJECTIVE
  To evaluate the relationship between initial and retreatment ablation centers in active eye-tracker-assisted myopic laser in situ keratomileusis (LASIK) and determine whether the relationship between the 2 ablation centers influences the visual outcome after retreatment.
  
  
  METHODS
  Department of Ophthalmology, China Medical University Hospital, Taichung, Taiwan.
  
  
  METHODS
  This retrospective study comprised 21 eyes of 15 patients who had retreatment at least 3 months after primary myopic LASIK by lifting the initial flap. Corneal topography and best corrected visual acuity (BCVA) were evaluated preoperatively and 3 months postoperatively. The ablation centration was analyzed by corneal topography preoperatively and at 3 months.
  
  
  RESULTS
  The mean decentration of the primary treatment was 0.43 mm +/- 0.21 (SD) and of the retreatment, 0.34 +/- 0.15 mm. There was no significant difference between them (P =.07). The 2 ablation centers were close each other. The mean distance between the 2 ablation centers was 0.29 +/- 0.18 mm and the mean angle between them, 39.7 +/- 46.2 degrees. The BCVA was unchanged after retreatment regardless of the relationship between the 2 ablation centers.
  
  
  CONCLUSIONS
  With an active eye-tracking system, the retreatment center was not only close to the pupil center but also close to the primary ablation center. Regardless of the relationship between the 2 ablation centers, the BCVA did not change if the retreatment ablation was well centered.
authors.affiliation: Department of Ophthalmology, China Medical University Hospital, 2 Yuh-Der Road, Taichung, Taiwan. yiyutsai@seed.net.tw
authors.forename: Yi-Yu
authors.initials: YY
authors.lastname: Tsai
authors.forename: Sung-Huei
authors.initials: SH
authors.lastname: Tseng
authors.forename: Jane-Ming
authors.initials: JM
authors.lastname: Lin
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology / Q000601:surgery*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000473:pathology / Q000601:surgery*; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology