title: Effects of decentration of photorefractive keratectomy on the induction of higher order wavefront aberrations.
abstract: OBJECTIVE
  To evaluate the effects of ablation decentration on the induction of higher order wavefront aberrations (HOAs) in active eye-tracker-assisted myopic photorefractive keratectomy (PRK) using the VISX STAR S4 laser with ActiveTrak (Abbott Medical Optics [AMO]).
  
  
  METHODS
  Ninety-four myopic eyes (53 patients) were divided into three groups according to ablation decentration (group 1, ≤0.15 mm, 20 eyes; group 2, >0.15 to ≤0.30 mm, 54 eyes; and group 3, >0.30 mm, 20 eyes). The distances of ablation centers from the centers of the entrance pupils were analyzed using corneal topography. Wavefront errors were measured preoperatively and at 6 months after PRK using a VISX WaveScan aberrometer (AMO). Statistical analysis was performed to assess the influence of ablation decentration on PRK-induced HOAs.
  
  
  RESULTS
  The mean decentration was 0.23±0.10 mm (range: 0.04 to 0.52 7 mm). The magnitude of all HOAs was significantly increased at 6 months postoperatively (P<.05). Increases in PRK-induced HOAs including total HOA, coma, and spherical aberration were significantly different among the three groups (P<.05). Statistically significant differences were noted between pairs of data in group 1 versus group 3 for total HOA (P=.015), coma (P=.038), and spherical aberration (P=.038), and group 2 versus group 3 for coma (P=.049).
  
  
  CONCLUSIONS
  Ablation decentration >0.30 mm from the center of the entrance pupil was associated with greater induction of total HOA, coma, and spherical aberration after PRK, as compared with ablation decentration <0.15 mm. In addition, ablation decentration has a more significant influence on coma-inducing effects.
authors.affiliation: Department of Ophthalmology, Yeungnam University College of Medicine, Daegu, Korea. sbummlee@med.yu.ac.kr
authors.forename: Sang-Bumm
authors.initials: SB
authors.lastname: Lee
authors.forename: Bo-Sung
authors.initials: BS
authors.lastname: Hwang
authors.forename: Junyeop
authors.initials: J
authors.lastname: Lee
mesh_terms: D057128:Aberrometry; D000328:Adult; D019781:Corneal Topography; D057108:Corneal Wavefront Aberration / Q000209:etiology*; D005260:Female; D019466:Glare; D006801:Humans; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D009887:Ophthalmoscopy; D018903:Photorefractive Keratectomy / Q000009:adverse effects*; D011680:Pupil / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult