title: Absolute color scale for improved diagnostics with wavefront error mapping.
abstract: OBJECTIVE
  Wavefront data are expressed in micrometers and referenced to the pupil plane, but current methods to map wavefront error lack standardization. Many use normalized or floating scales that may confuse the user by generating ambiguous, noisy, or varying information. An absolute scale that combines consistent clinical information with statistical relevance is needed for wavefront error mapping. The color contours should correspond better to current corneal topography standards to improve clinical interpretation.
  
  
  METHODS
  Retrospective analysis of wavefront error data.
  
  
  METHODS
  Historic ophthalmic medical records.
  
  
  METHODS
  Topographic modeling system topographical examinations of 120 corneas across 12 categories were used. Corneal wavefront error data in micrometers from each topography map were extracted at 8 Zernike polynomial orders and for 3 pupil diameters expressed in millimeters (3, 5, and 7 mm). Both total aberrations (orders 2 through 8) and higher-order aberrations (orders 3 through 8) were expressed in the form of frequency histograms to determine the working range of the scale across all categories. The standard deviation of the mean error of normal corneas determined the map contour resolution. Map colors were based on corneal topography color standards and on the ability to distinguish adjacent color contours through contrast.
  
  
  METHODS
  Higher-order and total wavefront error contour maps for different corneal conditions.
  
  
  RESULTS
  An absolute color scale was produced that encompassed a range of +/-6.5 microm and a contour interval of 0.5 microm. All aberrations in the categorical database were plotted with no loss of clinical information necessary for classification. In the few instances where mapped information was beyond the range of the scale, the type and severity of aberration remained legible.
  
  
  CONCLUSIONS
  When wavefront data are expressed in micrometers, this absolute scale facilitates the determination of the severity of aberrations present compared with a floating scale, particularly for distinguishing normal from abnormal levels of wavefront error. The new color palette makes it easier to identify disorders. The corneal mapping method can be extended to mapping whole eye wavefront errors. When refraction data are expressed in diopters, the previously published corneal topography scale is suggested.
authors.affiliation: Department of Ophthalmology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA. msmole@lsuhsc.edu
authors.forename: Michael K
authors.initials: MK
authors.lastname: Smolek
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Klyce
mesh_terms: D003116:Color / Q000592:standards*; D003315:Cornea / Q000033:anatomy & histology / Q000473:pathology*; D003316:Corneal Diseases / Q000175:diagnosis*; D019781:Corneal Topography / Q000592:standards*; D006801:Humans; D012015:Reference Standards; D012030:Refractive Errors / Q000175:diagnosis*; D012189:Retrospective Studies; D014481:United States