Design, characterization and visual performance of a new multizone   contact lens
  Objectives: To analyze the whole process involved in the production of a new bifocal Multizone Contact Lens (MCL) for presbyopia.   Methods: The optical quality of a new MCL was evaluated by ray tracing software in a model eye with pupil different diameters with the lens centered and decentered. A stock of low addition (+1.5 D) MCL for presbyopia was ordered for manufacturing. Power profiles were measured with a contact lens power mapper, processed with a custom software and compared with the theoretical design. Nine lenses from the stock were fitted to presbyopic subjects and the visual performance was evaluated with new APPs for iPad Retina.   Results: Numerical simulations showed that the trough the focus curve provided by MCL has an extended depth of focus. The optical quality was not dependent on pupil size and only decreased for lens decentered with a pupil diameter of 4.5 mm. The manufactured MCL showed a smoothed power profile with a less-defined zones. The bias between experimental and theoretical zone sizes was uniform along the optical zone unless for the most central area. Eyes fitted with the manufactured MCL showed an improvement in near Visual Acuity (VA) and near stereopsis. Althouh Contrast Sensitivity (CS) at distance decreased, the defocus curve for contrast showed an extended depth of focus correlated to the ray tracing results.   Conclusions: The understanding of vision with MCL requires a process that involves design and characterization for detecting any defect that may have impact in the final visual performance. Keywords: Multifocal contact lenses, design, characterization, visual performance 
Manuel Rodriguez-Vallejo, Clara Llorens-Quintana, Juan A. Monsoriu and   Walter D. Furlan
physics.med-ph