title: Zonal matrix iterative method for wavefront reconstruction from gradient measurements.
abstract: OBJECTIVE
  To present an alternate method to Zemike decomposition (modal) of wavefront reconstruction using iterative implicit solution to the finite difference equations (zonal).
  
  
  METHODS
  Different reconstruction methods, modal and zonal, were compared and the advantages of each method were analyzed.
  
  
  RESULTS
  Although the modal or Zemike method allows for quantitative interpretation of some of the aberrations, it is cumbersome for use with fine details and may lead to errors for eyes with keratoconus or other rapidly varying aberration. The zonal method produces a very high-resolution map that can be used for identifying irregular structures.
  
  
  CONCLUSIONS
  The distinction between the two methods is useful to maintain, and the solution methods are generally different. In practice, both methods are useful and, with modern computers, both zonal and lower-order modal may be calculated rapidly. The difference between the wavefronts derived from the two methods may provide useful insight or interpretation of the infornation.
authors.affiliation: Department of Ophthalmology, University of Crete Medical School, Crete, Greece. spanagop@med.uoc.gr
authors.forename: Sophia I
authors.initials: SI
authors.lastname: Panagopoulou
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Neal
mesh_terms: D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography / Q000379:methods*; D006801:Humans; D008433:Mathematics; D015233:Models, Statistical; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000175:diagnosis*