title: Tracker-assisted versus manual ablation zone centration in laser in situ keratomileusis for myopia and astigmatism.
abstract: OBJECTIVE
  Eye tracker systems have been developed concomitantly with small scanning beams to theoretically reduce ablation zone decentration and for accurate registration of all the laser pulses on the cornea. The purpose of the study was to compare the tracker-assisted with the manual centration method.
  
  
  METHODS
  Twenty-five patients (48 eyes) with myopia and/or astigmatism had laser in situ keratomileusis (LASIK) between August 1998 and February 1999 with the Technolas 117C laser. Twenty patients (38 eyes, 80%) were available for follow-up at 3 months after surgery. Eyes were assigned randomly to one of two ablation zone centration methods: Group 1: Tracker-assisted (20 eyes), Group 2: Manual (18 eyes).
  
  
  RESULTS
  Mean distance between the ablation zone center and the pupillary center in the tracker-assisted centration group was 0.55 +/- 0.30 mm (range, 0.10 to 1.4 mm), and in the manual centration group, 0.43 +/- 0.23 mm (range, 0.10 to 1.0 mm) (P = .177). There was no statistically significant difference in postoperative contrast sensitivity, glare, and Topographical Corneal Surface Regularity Index (SRI) between the two groups.
  
  
  CONCLUSIONS
  We obtained good results with both centration methods. We did not find superiority of the tracker-assisted over manual regarding ablation zone centration, vision quality, or regularity of the ablation.
authors.affiliation: Clínica de Oftalmología, Carrera 47 # 8C-94, Cali, Colombia, South America. ospinero@mafalda.univalle.edu.co
authors.forename: Oscar E
authors.initials: OE
authors.lastname: Pineros
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D015350:Contrast Sensitivity; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000295:instrumentation / Q000379:methods*; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D012029:Refraction, Ocular; D014792:Visual Acuity