title: Repeatability of measurements obtained with a ray tracing aberrometer.
abstract: OBJECTIVE
  To evaluate the repeatability of ocular aberrometry at distance and near vision conditions provided by the latest version of a ray tracing aberrometer.
  
  
  METHODS
  A total of 22 healthy eyes of 22 patients with ages ranging from 21 to 65 years were included in this study. All eyes achieved a best spectacle corrected visual acuity of 20/20, and had not undergone previous ocular surgeries. Three consecutive aberrometric measurements were obtained with the iTrace system (Tracey Technologies) by an experienced examiner at distance (5 m) and near (40 cm).
  
  
  RESULTS
  Low values of within-subject standard deviation (Sw) were found for sphere and cylinder at distance and near and for the power vector components of refraction. However, a more pronounced variability was observed for the coefficients associated with higher order aberrations, with the poorest repeatability for the vertical coma at near, Sw of 0.011 μm for a mean value of 0.018 μm. Additionally, Sw for vertical coma was significantly larger at near (p = 0.01). No significant differences between the distance and near values of Sw for the power vector components of refraction were found (p ≥ 0.08). The Sw values for the distance and near modulation transfer function parameters were low when compared with their corresponding mean values.
  
  
  CONCLUSIONS
  The iTrace system provides repeatable measurements of the spherocylindrical refraction at near and distance, but consistency of aberrometric and optical quality measurements seems to be limited.
authors.affiliation: Vissum/Instituto Oftalmológico de Alicante, Alicante, Spain. david.pinyero@ua.es
authors.forename: David P
authors.initials: DP
authors.lastname: Piñero
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Sánchez-Pérez
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Alió
mesh_terms: D057128:Aberrometry / Q000379:methods*; D000328:Adult; D000368:Aged; D005123:Eye / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000175:diagnosis* / Q000503:physiopathology; D014787:Vision Tests; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult