title: Optical power distribution of refractive and aspheric multifocal contact lenses: Effect of pupil size.
abstract: OBJECTIVE
  To evaluate the power profile within the optic zone of different designs of multifocal contact lenses (CLs) and to analyze how the effect of pupil size could impact on their optical performance.
  
  
  METHODS
  The optical power distribution within the optic zones of multifocal CLs was measured by the Nimo TR1504 (LAMBDA-X, Belgium). The multifocal CLs under study were the Acuvue Bifocal, the Acuvue Oasys for Presbyopia, the PureVision Multifocal and the PureVision 2 for Presbyopia. Each design was considered in all their available addition powers. All lenses had a nominal power of -3.0D. At the same time, three lenses of each model were considered and five consecutive readings of each lens were performed.
  
  
  RESULTS
  The results show that the PureVision Multifocal and the PureVision 2 for Presbyopia have aspheric power profiles. Both designs showed aspheric center-near designs with a smoother progression of the optical power in the PureVision 2 for Presbyopia. The Acuvue Bifocal and the Acuvue Oasys for Presbyopia are shown to have concentric alternating near and far zones. Apart from the refractive rings, the Acuvue Oasys for Presbyopia showed an increase in negative (or less positive) values toward the periphery of the lens.
  
  
  CONCLUSIONS
  Besides the refraction, the knowledge of the power profiles of multifocal CLs and the effect of pupil size on the optical distribution of these lenses could be crucial to understand the performance of these designs when they are fitted.
authors.affiliation: Optometry Research Group (GIO), Optics Department, University of Valencia, Spain. Electronic address: david.madrid@uv.es.
authors.forename: D
authors.initials: D
authors.lastname: Madrid-Costa
authors.affiliation: Optometry Research Group (GIO), Optics Department, University of Valencia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Ruiz-Alcocer
authors.affiliation: Optometry Research Group (GIO), Optics Department, University of Valencia, Spain.
authors.forename: S
authors.initials: S
authors.lastname: García-Lázaro
authors.affiliation: Optometry Research Group (GIO), Optics Department, University of Valencia, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Ferrer-Blasco
authors.affiliation: Optometry Research Group (GIO), Optics Department, University of Valencia, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Montés-Micó
mesh_terms: D003261:Contact Lenses / Q000145:classification*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D008027:Light; D011305:Presbyopia / Q000534:rehabilitation*; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation
keywords: In vitro; Multifocal contact lenses; Power profile; Pupil diameter