title: Power profiles and short-term visual performance of soft contact lenses.
abstract: OBJECTIVE
  To investigate the manner in which contemporary soft contact lenses differ in the distribution of optical power within their optic zones and establish if these variations affect the vision of wearers or the prescribing procedure for back vertex power (BVP).
  
  
  METHODS
  By using a Visionix VC 2001 contact lens power analyzer, power profiles were measured across the optic zones of the following contemporary contact lenses ACUVUE 2, ACUVUE ADVANCE, O2OPTIX, NIGHT & DAY and PureVision. Single BVP measures were obtained using a Nikon projection lensometer. Visual performance was assessed in 28 masked subjects who wore each lens type in random order. Measurements taken were high and low contrast visual acuity in normal illumination (250 Cd/m), high contrast acuity in reduced illumination (5 Cd/m), subjective visual quality using a numerical rating scale, and visual satisfaction rating using a Likert scale.
  
  
  RESULTS
  Marked differences in the distribution of optical power across the optic zone were evident among the lens types. No significant differences were found for any of the visual performance variables (p > 0.05, analysis of variance with repeated measures and Friedman test).
  
  
  CONCLUSIONS
  Variations in power profile between contemporary soft lens types exist but do not, in general, result in measurable visual performance differences in the short term, nor do they substantially influence the BVP required for optimal correction.
authors.affiliation: Institute for Eye Research, Sydney, New South Wales, Australia. e.papas@ier.org.au
authors.forename: Eric
authors.initials: E
authors.lastname: Papas
authors.forename: Anne
authors.initials: A
authors.lastname: Dahms
authors.forename: Nicole
authors.initials: N
authors.lastname: Carnt
authors.forename: Nina
authors.initials: N
authors.lastname: Tahhan
authors.forename: Klaus
authors.initials: K
authors.lastname: Ehrmann
mesh_terms: D000704:Analysis of Variance; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D008297:Male; D055620:Optical Phenomena; D055095:Optics and Photonics / Q000379:methods; D012031:Refractometry; D016037:Single-Blind Method; D013997:Time Factors; D014785:Vision, Ocular