title: Clinical evaluation of the Shin-Nippon NVision-K 5001/Grand Seiko WR-5100K autorefractor.
abstract: OBJECTIVE
  A clinical evaluation of the Shin-Nippon NVision-K 5001 (also branded as the Grand Seiko WR-5100K) autorefractor (Japan) was performed to examine validity and repeatability compared with subjective refraction and Javal-Schiotz keratometry.
  
  
  METHODS
  Measurements of refractive error were performed on 198 eyes of 99 subjects (aged 23.2 +/- 7.4 years) subjectively (noncycloplegic) by one masked optometrist and objectively with the NVision-K autorefractor by a second optometrist. Keratometry measurements using the NVision-K were compared with the Javal-Schiotz keratometer. Intrasession repeatability of the NVision-K was also assessed on all 99 subjects together with intersession repeatability on a separate occasion separated by 7 to 14 days.
  
  
  RESULTS
  Refractive error as measured by the NVision-K was found to be similar (p = 0.67) to subjective refraction (difference, 0.14 +/- 0.35 D). It was both accurate and repeatable over a wide prescription range (-8.25 to +7.25 D). Keratometry as measured by the NVision-K was found to be similar (p > 0.50) to the Javal-Schiotz technique in both the horizontal and vertical meridians (horizontal: difference, 0.02 +/- 0.09 mm; vertical: difference, 0.01 +/- 0.14 mm). There was minimal bias, and the results were repeatable (horizontal: intersession difference, 0.00 +/- 0.09 mm; vertical: intersession difference, -0.01 +/- 0.12 mm).
  
  
  CONCLUSIONS
  The open-view arrangement of the Shin-Nippon NVision-K 5001 facilitates the measurement of static refractive error and the accommodative response to real-world stimuli. Coupled with its accuracy, repeatability, and capability to measure corneal curvature, it is a valuable addition to objective instrumentation currently available to the optometrist and researcher.
authors.affiliation: Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham, United Kingdom.
authors.forename: Leon Nicholas
authors.initials: LN
authors.lastname: Davies
authors.forename: Edward Arthur Harry
authors.initials: EA
authors.lastname: Mallen
authors.forename: James Stuart
authors.initials: JS
authors.lastname: Wolffsohn
authors.forename: Bernard
authors.initials: B
authors.lastname: Gilmartin
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009907:Optometry / Q000295:instrumentation*; D011237:Predictive Value of Tests; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000175:diagnosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015351:Vision Screening / Q000295:instrumentation*