title: Precision of higher order aberration repeatability with NIDEK OPD-scan retinoscopic aberrometry.
abstract: OBJECTIVE
  To evaluate repeatability of the total high order aberrations with a retinoscopic wavefront sensor.
  
  
  METHODS
  This prospective case series analyzed 12 eyes from 6 patients who underwent wavefront measurement using retinoscopic aberrometry with the NIDEK Optical Path Difference Scan (OPD-Scan). Four consecutive wavefront measurements of each eye were taken by two trained examiners for 5.8+/-0.8-mm and 8.2+/-0.6-mm pupils (P=.002, Wilcoxon test). Total high order aberrations out to the eighth order were assessed including third order coma, third order trefoil, fourth order quadrafoil, fourth order secondary astigmatism, and fourth order spherical aberrations. Differences between measurements of all of the variables were analyzed. A P value <.05 was considered statistically significant.
  
  
  RESULTS
  Repeatability analysis of the root-mean-square of total higher order aberrations, coma, trefoil, quadrafoil, secondary astigmatism, and spherical aberrations for both dilated and nondilated pupils did not show a statistically significant difference among all repeated measurements, except for trefoil and secondary astigmatism (analysis of variance and the Friedman test). The repeatability of total higher order aberrations was 0.15 microm for nondilated pupils and 0.18 microm for dilated pupils. Except for trefoil measurements, all high order aberrations showed reproducibility >0.15 microm when Zernike coefficients were analyzed individually.
  
  
  CONCLUSIONS
  The NIDEK OPD-Scan aberrometer measures total higher order astigmatism and most individual aberrations with acceptable repeatability. However, measurement of trefoil with this instrument is less repeatable.
authors: Department of Ophthalmology, University of São Paulo, Brazil.
authors: Jackson
authors: J
authors: Barreto
authors: Marcelo V
authors: MV
authors: Netto
authors: Alberto
authors: A
authors: Cigna
authors: Samir
authors: S
authors: Bechara
authors: Newton
authors: N
authors: Kara-José
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D018903:Photorefractive Keratectomy / Q000379:methods; D011300:Preoperative Care; D011379:Prognosis; D011446:Prospective Studies; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D042261:Retinoscopes; D042262:Retinoscopy / Q000379:methods*