title: Comparison of near fusional vergence ranges with rotary prisms and with prism bars.
abstract: BACKGROUND
  Common methods for determination of fusional vergence ranges make use of rotary prisms in the phoropter or prism bars out of the phoropter. This study compared near fusional vergence ranges with rotary prisms with those with prism bars.
  
  
  METHODS
  Fifty young adults served as subjects. Odd-numbered subjects had rotary prism vergences performed before prism bar vergences. For even-numbered subjects, prism bar vergences were done first. Base-in (BI) vergences were done before base-out (BO) vergences with both rotary prisms and prism bars. A coefficient of agreement was calculated by multiplying the standard deviation of the individual subject differences between rotary prisms and prism bars by 1.96, to approximate the range within which the 2 tests would agree 95% of the time.
  
  
  RESULTS
  The lowest coefficient of agreement was 7.3Δ for the BI recovery. The others were high, ranging from 15.4Δ for the BO recovery to 19.5Δ for the BO break.
  
  
  CONCLUSIONS
  Fusional vergence ranges determined by prism bars out of the phoropter cannot be used interchangeably with those determined by phoropter rotary prisms for the purpose of follow-up on individual patients or for the purpose of comparison with norms.
authors.affiliation: School of Optometry, Indiana University, Bloomington, Indiana 47405, USA. dgoss@indiana.edu
authors.forename: David A
authors.initials: DA
authors.lastname: Goss
authors.forename: Emily
authors.initials: E
authors.lastname: Becker
mesh_terms: D003290:Convergence, Ocular; D004867:Equipment Design / Q000592:standards; D006801:Humans; D007909:Lenses; D014787:Vision Tests / Q000295:instrumentation*; D015348:Vision, Binocular; D055815:Young Adult