title: Wavefront-guided multipoint (segmental) custom ablation enhancement using the Nidek NAVEX platform.
abstract: OBJECTIVE
  To present our clinical experience regarding enhancement (retreatment) of previously performed non-wavefront-guided refractive surgery by wavefront-guided multipoint (segmental) custom ablation utilizing the Nidek NAVEX platform.
  
  
  METHODS
  Retrospective clinical analysis was conducted of 20 eyes (19 patients) with mixed myopic or hyperopic astigmatism who had undergone primary laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) and reported postoperative reductions in quality of vision. These vision disturbances correlated with clinically significant elevations in the root mean square of higher order aberrations (RMS of HOA) values. Before wavefront-guided multipoint (segmental) custom ablation enhancement with the NAVEX platform, all patients underwent testing with the Nidek Optical Path Difference Scan (OPD-Scan) and analysis with Final Fit Software.
  
  
  RESULTS
  Twenty eyes showed improvement or resolution of visual symptoms following wavefront-guided multipoint (segmental) custom ablation enhancement. The postoperative root mean square of higher order aberration values were variable and not always related to improvement in visual function. No patient lost two or more lines of best spectacle-corrected visual acuity.
  
  
  CONCLUSIONS
  Topography and wavefrontguided multipoint (segmental) custom ablation enhancements were safe and effective in improving visual symptoms following primary refractive surgery. In some eyes, improved visual function without correspondingly lower RMS of HOA values may be an effect of neutralizing some chromatic aberrations across the visible light spectrum, thereby improving the modulation transfer function.
authors.affiliation: Gimbel Eye Centre, Calgary, Alberta, Canada. hvgimbel@gimbel.com
authors.forename: Howard V
authors.initials: HV
authors.lastname: Gimbel
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Sofinski
authors.forename: Oron S
authors.initials: OS
authors.lastname: Mahler
authors.forename: John A
authors.initials: JA
authors.lastname: van Westenbrugge
authors.forename: Maria I
authors.initials: MI
authors.lastname: Ferensowicz
authors.forename: Rick W
authors.initials: RW
authors.lastname: Triebwasser
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000601:surgery*; D003319:Corneal Stroma / Q000601:surgery; D019781:Corneal Topography / Q000379:methods; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000601:surgery*; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011183:Postoperative Complications; D012029:Refraction, Ocular; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D012449:Safety; D016896:Treatment Outcome; D014792:Visual Acuity