title: Visual acuity through fresnel, refractive, and hybrid diffractive/refractive prisms.
abstract: BACKGROUND
  This article compares the effect on visual acuity of the Fresnel and wedge-shaped refractive prisms with newly developed hybrid diffractive/refractive prisms (ComPrisms), which combine a wedge-shaped refractive prism with a diffractive component. The diffractive component of hybrid elements can be designed to correct the chromatic aberration of the refractive component.
  
  
  METHODS
  The monocular visual acuity of 21 subjects and binocular acuity of 20 subjects were measured with computer-generated logMAR charts. Visual acuity was measured without prisms (NP) and through ComPrisms, 3M Press-on Fresnel, and acrylic refractive prisms of 20delta, 30delta, and 40delta powers.
  
  
  RESULTS
  A repeated measures analysis of variance indicates a significant main effect of treatment (without prisms and through the three types of prisms) at each prism power, both monocularly and binocularly. Results of the Scheffé test for all possible comparisons between pairs of means of the treatments are provided.
  
  
  CONCLUSIONS
  Although all the prisms reduced visual acuity, the ComPrisms provide significantly better visual acuity than acrylic refractive or 3M Press-on Fresnel prisms of equivalent power
authors.affiliation: State University of New York, College of Optometry, New York, New York 10036, USA. mkatz@sunyopt.edu
authors.forename: Milton
authors.initials: M
authors.lastname: Katz
mesh_terms: D000328:Adult; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008297:Male; D015348:Vision, Binocular / Q000502:physiology; D015349:Vision, Monocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology*