title: Compensation of aniseikonia with toric intraocular lenses and spherocylindrical spectacles.
abstract: OBJECTIVE
  Magnification disparity between the two eyes (aniseikonia) is one of the major unresolved problems in modern cataract surgery, potentially degrading binocular visual function or causing diplopia. The purpose of this study is to describe a paraxial computing scheme using 4x4 system matrices to simulate a corrected pseudophakic 'optical system eye' with a meridional magnification that matches the magnification of a given contralateral eye.
  
  
  METHODS
  Based on the definition of a centred optical system in the paraxial Gaussian space containing astigmatic surfaces using 4x4 refraction and translation matrices, we derived a methodology for calculating the refractive power and axis of toric intraocular lenses and spherocylindrical spectacle corrections for (i) fully correcting the optical system eye and (ii) realizing an arbitrary meridional magnification by solving a linear equation system.
  
  
  RESULTS
  The capabilities of this computing scheme are demonstrated with two examples. In example 1 we calculate a toric lens and a spherocylindrical spectacle correction for compensation of a corneal astigmatism to realize a predefined iso-meridional magnification. In example 2 we first determine the meridional magnification of the contralateral eye, which has been treated with cataract surgery and toric lens implantation, and then we compute the appropriate combination of a fully correcting toric lens and spherocylindrical spectacle refraction, which exactly matches the meridional magnification of the contralateral eye.
  
  
  CONCLUSIONS
  We presented an en bloc matrix based strategy for the calculation of an optical system eye containing an astigmatic cornea, a toric lens implant and a spherocylindrical spectacle correction, where the toric lens and the spherocylindrical spectacle correction are determined to fully correct the system and to realize an arbitrary meridional magnification i.e. to eliminate aniseikonia.
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nürnberg, Schwabachanlage 6, D-91054 Erlangen, Germany. achim.langenbucher@augen.imed.uni-erlangen.de
authors.forename: Achim
authors.initials: A
authors.lastname: Langenbucher
authors.forename: Sven
authors.initials: S
authors.lastname: Reese
authors.forename: Stefan
authors.initials: S
authors.lastname: Huber
authors.forename: Berthold
authors.initials: B
authors.lastname: Seitz
mesh_terms: D000839:Aniseikonia / Q000503:physiopathology / Q000628:therapy*; D001251:Astigmatism / Q000503:physiopathology / Q000628:therapy; D003198:Computer Simulation; D005139:Eyeglasses; D006801:Humans; D007910:Lenses, Intraocular; D008954:Models, Biological; D055095:Optics and Photonics; D011474:Prosthesis Design / Q000379:methods; D019591:Pseudophakia / Q000503:physiopathology / Q000628:therapy; D012029:Refraction, Ocular