title: Power profiles of single vision and multifocal soft contact lenses.
abstract: OBJECTIVE
  The purpose of this study was to investigate the optical zone power profile of the most commonly prescribed soft contact lenses to assess their potential impact on peripheral refractive error and hence myopia progression.
  
  
  METHODS
  The optical power profiles of six single vision and ten multifocal contact lenses of five manufacturers in the powers -1.00 D, -3.00 D, and -6.00 D were measured using the SHSOphthalmic (Optocraft GmbH, Erlangen, Germany). Instrument repeatability was also investigated.
  
  
  RESULTS
  Instrument repeatability was dependent on the distance from the optical centre, manifesting unreliable data for the central 1mm of the optic zone. Single vision contact lens measurements of -6.00 D lenses revealed omafilcon A having the most negative spherical aberration, lotrafilcon A having the least. Somofilcon A had the highest minus power and lotrafilcon A the biggest deviation in positive direction, relative to their respective labelled powers. Negative spherical aberration occurred for almost all of the multifocal contact lenses, including the centre-distance designs etafilcon A bifocal and omafilcon A multifocal. Lotrafilcon B and balafilcon A seem to rely predominantly on the spherical aberration component to provide multifocality.
  
  
  CONCLUSIONS
  Power profiles of single vision soft contact lenses varied greatly, many having a negative spherical aberration profile that would exacerbate myopia. Some lens types and powers are affected by large intra-batch variability or power offsets of more than 0.25 dioptres. Evaluation of power profiles of multifocal lenses was derived that provides helpful information for prescribing lenses for presbyopes and progressing myopes.
authors.affiliation: Aalen University, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Wagner
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Fabian
authors.initials: F
authors.lastname: Conrad
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Ravi C
authors.initials: RC
authors.lastname: Bakaraju
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Cathleen
authors.initials: C
authors.lastname: Fedtke
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, Australia. Electronic address: k.ehrmann@brienholdenvision.org.
authors.forename: Klaus
authors.initials: K
authors.lastname: Ehrmann
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Brien A
authors.initials: BA
authors.lastname: Holden
mesh_terms: D003263:Contact Lenses, Hydrophilic; D004867:Equipment Design; D006801:Humans; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology / Q000628:therapy*; D015203:Reproducibility of Results
keywords: Multifocal contact lenses; Power profiles; Soft contact lenses; Spherical aberration