title: Polar value analysis of refractive data.
abstract: OBJECTIVE
  To demonstrate the use of polar value analysis of surgically induced astigmatism (SIA).
  
  
  METHODS
  Department of Ophthalmology, Arhus University Hospital, Arhus, Denmark.
  
  
  METHODS
  Univariate polar value analysis of SIA was demonstrated for a single patient and for aggregate data. Bivariate polar value analysis was performed for aggregate data.
  
  
  RESULTS
  The meridional polar value AKP expresses the surgically induced flattening, while the oblique polar value AKP(+45) indicates the torque. This pair of polar values characterizes a regular astigmatism completely. In bivariate polar value analysis, the average SIA is the combined mean for AKP and AKP(+45), while the spread is a confidence area delineated by an ellipse.
  
  
  CONCLUSIONS
  Univariate and bivariate polar value analyses, together with the surgically induced change in spherical equivalent power, yield an exact description of surgically induced change following refractive procedures.
authors.affiliation: Department Ophthalmology, Arhus University Hospital, Arhus, Denmark. RC.POST.173@aaa.dk
authors.forename: K
authors.initials: K
authors.lastname: Naeser
authors.forename: J
authors.initials: J
authors.lastname: Hjortdal
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis* / Q000209:etiology; D003315:Cornea / Q000473:pathology* / Q000601:surgery; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*