title: Evaluation of the auto-refraction function of the Nidek OPD-Scan III.
abstract: BACKGROUND
  The aim was to evaluate the validity and repeatability of the auto-refraction function of the Nidek OPD-Scan III (Nidek Technologies, Gamagori, Japan) compared with non-cycloplegic subjective refraction. The Nidek OPD-Scan III is a new aberrometer/corneal topographer workstation based on the skiascopy principle. It combines a wavefront aberrometer, topographer, autorefractor, auto keratometer and pupillometer/pupillographer.
  
  
  METHODS
  Objective refraction results obtained using the Nidek OPD-Scan III were compared with non-cycloplegic subjective refraction for 108 eyes of 54 participants (29 female) with a mean age of 23.7 ± 9.5 years. Intra-session and inter-session variability were assessed on 14 subjects (28 eyes).
  
  
  RESULTS
  The Nidek OPD-Scan III gave slightly more negative readings than results obtained by subjective refraction (Nidek mean difference -0.19 ± 0.36 DS, p < 0.01 for sphere; -0.19 ± 0.35 DS, p < 0.01 for mean spherical equivalent; -0.002 ± 0.23 DC, p = 0.91 for cylinder; -0.06 ± 0.38 DC, p = 0.30 for J0 and -0.36 ± 0.31 DC for J45, p = 0.29). Auto-refractor results for 74 per cent of spherical readings and 60 per cent of cylindrical powers were within ± 0.25 of subjective refraction. There was high intra-session and inter-session repeatability for all parameters; 90 per cent of inter-session repeatability results were within 0.25 D.
  
  
  CONCLUSIONS
  The Nidek OPD-Scan III gives valid and repeatable measures of objective refraction when compared with non-cycloplegic subjective refraction.
authors.affiliation: Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom. s.mcginnigle@aston.ac.uk.
authors.forename: Samantha
authors.initials: S
authors.lastname: McGinnigle
authors.forename: Shehzad A
authors.initials: SA
authors.lastname: Naroo
authors.forename: Frank
authors.initials: F
authors.lastname: Eperjesi
mesh_terms: D000328:Adult; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000175:diagnosis*; D015203:Reproducibility of Results; D014792:Visual Acuity
keywords: aberrometer; refraction; refractive error