title: Correlation of Nidek OPD-Scan objective refraction with subjective refraction.
abstract: OBJECTIVE
  The aim of this study was to quantify how closely the Nidek OPD-Scan objective refraction correlated with subjective refraction.
  
  
  METHODS
  A retrospective audit of the preoperative refraction of 80 myopic and myopic astigmatic eyes before laser in situ keratomileusis (LASIK) or laser supepithelial keratomileusis (LASEK) was performed. Objective refraction in the 5-mm zone was performed using a Nidek OPD-Scan. Subjective refraction was performed by a senior optometrist. Statistical analysis of sphere, cylinder, and spherical equivalent refraction measurements was then performed.
  
  
  RESULTS
  Spherical measurements correlated well with a linear regression equation, with a correlation coefficient of 0.97. Cylinder measurements correlated less well, with a correlation coefficient of 0.85. Spherical equivalent refraction measurements correlated well, with a correlation coefficient of 0.97. Analyzing the numerical difference between each objective refraction and its corresponding subjective refraction, the majority of values were only 0.50 D apart for sphere, cylinder, and spherical equivalent refraction.
  
  
  CONCLUSIONS
  There was good correlation between objective OPD-Scan and subjective refraction, especially for sphere and spherical equivalent refraction measurements, with regression gradients and correlation coefficients close to 1.
authors.affiliation: Midland Eye Institute, West Midlands, UK.
authors.forename: Ian Y L
authors.initials: IY
authors.lastname: Yeung
authors.forename: Sanjay
authors.initials: S
authors.lastname: Mantry
authors.forename: Ian A
authors.initials: IA
authors.lastname: Cunliffe
authors.forename: Mark T
authors.initials: MT
authors.lastname: Benson
authors.forename: Sunil
authors.initials: S
authors.lastname: Shah
mesh_terms: D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D049008:Keratectomy, Subepithelial, Laser-Assisted / Q000379:methods*; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D012029:Refraction, Ocular / Q000502:physiology*; D012189:Retrospective Studies