title: Quantitative performance of bifocal and multifocal intraocular lenses in a model eye: point spread function in multifocal intraocular lenses.
abstract: OBJECTIVE
  To compare the optical properties of bifocal diffractive and multifocal refractive intraocular lenses.
  
  
  METHODS
  A model eye with a pupil 4.5 mm in diameter was used to determine the point spread function (PSF) of the distance focus and near focus of a diffractive bifocal intraocular lens (IOL) (model 811E; Pharmacia Inc, Columbus, Ohio) and of a refractive multifocal IOL (model SA40N; Allergan Optical Inc, Irvine, Calif) to compare them with PSFs of foci of corresponding monofocal lenses. For interpreting the PSFs the through focus response, the modulation transfer function, and the Strehl ratio were evaluated.
  
  
  RESULTS
  The intensity of the distance focus of the bifocal diffractive lens reached 58.5% and the near focus attained 42.7% of the intensity of a corresponding monofocal lens. The maximal halo intensity surrounding both foci was approximately 4.5%. The distance peak of the refractive multifocal IOL was 73.4% and the near peak 25.1% of a corresponding monofocal lens. The out-of-focus image overlaying the distance focus of the refractive multifocal IOL was approximately 3% of the light intensity of the distance focus, whereas the PSF of the near focus of the multifocal IOL is substantially affected by out-of-focus images. The computed modulation transfer functions show better results for the monofocal lenses, similar results for the tested distance foci, and clear advantages for the bifocal diffractive near focus.
  
  
  CONCLUSIONS
  Modulation transfer functions reveal comparable properties for distance vision and a superiority of the bifocal diffractive lens over the refractive multifocal lens for near vision.
authors.affiliation: Department of Ophthalmology, University of Vienna Medical School, Währinger Gürtel 18-20, 1090 Vienna, Austria. stefan.pieh@univie.ac.at
authors.forename: Stefan
authors.initials: S
authors.lastname: Pieh
authors.forename: Patrick
authors.initials: P
authors.lastname: Marvan
authors.forename: Birgit
authors.initials: B
authors.lastname: Lackner
authors.forename: Georg
authors.initials: G
authors.lastname: Hanselmayer
authors.forename: Gerald
authors.initials: G
authors.lastname: Schmidinger
authors.forename: Rainer
authors.initials: R
authors.lastname: Leitgeb
authors.forename: Markus
authors.initials: M
authors.lastname: Sticker
authors.forename: Christoph K
authors.initials: CK
authors.lastname: Hitzenberger
authors.forename: Adolf F
authors.initials: AF
authors.lastname: Fercher
authors.forename: Christian
authors.initials: C
authors.lastname: Skorpik
mesh_terms: D005123:Eye; D006801:Humans; D007910:Lenses, Intraocular; D008954:Models, Biological; D055095:Optics and Photonics