title: Validity of scaling zernike coefficients to a larger diameter for refractive surgery.
abstract: OBJECTIVE
  To investigate the validity of a Zernike rescaling algorithm to a larger wavefront diameter.
  
  
  METHODS
  Using 4256 preoperative wavefront examinations, the variability of inter-examination wavefront root-mean-square (RMS) was compared to the error induced due to scaling Zernike coefficients to a larger diameter. The validity of scaling Zernike coefficients was set when the error due to the scaling was the same as the variability of the inter-examination wavefronts. The inter-examination variability was calculated from eyes having at least 3 same-day, preoperative examinations over the same diameters. Error from scaling Zernike coefficients to a larger diameter was calculated by comparing the wavefront for a (scaled-up) set of Zernike coefficients to the wavefront of the average of Zernike coefficient sets at a larger diameter for the same eye. Wavefront diameters of 5, 5.5, 6, 6.5, and 7 mm were considered.
  
  
  RESULTS
  No significant difference was found for the variability for different pupil sizes. The error due to scaling Zernike coefficients to a larger pupil size was generally smaller than the inter-examination variability when the new diameter was 0.25 mm larger than the original diameter. The error was comparable to the inter-examination variability when the new diameter was 0.5 mm larger. The error became larger when the new diameter was >0.75 mm larger than the original diameter.
  
  
  CONCLUSIONS
  Rescaling Zernike coefficients from a smaller diameter to a larger one has practical applications in optical zone extension for wavefront-guided refractive surgery.
authors: Abbott Medical Optics Inc. Milpitas, California 95035, USA. george.dai@amo.aboott.com
authors: Guang-Ming
authors: GM
authors: Dai
mesh_terms: D057128:Aberrometry; D000465:Algorithms; D048988:Corneal Surgery, Laser; D057108:Corneal Wavefront Aberration / Q000175:diagnosis* / Q000601:surgery; D006801:Humans