title: Stereoscopic Viewing Can Induce Changes in the CA/C Ratio.
abstract: Stereoscopic displays challenge the neural cross-coupling between accommodation and vergence by inducing a constant accommodative demand and a varying vergence demand. Stereoscopic viewing calls for a decrease in the gain of vergence accommodation, which is the accommodation caused by vergence, quantified by using the convergence-accommodation to convergence (CA/C) ratio. However, its adaptability is still a subject of debate.
  
  
  
  Cross-coupling (CA/C and AC/A ratios) and tonic components of vergence and accommodation were assessed in 12 participants (27.5 ± 5 years, stereoacuity better than 60 arc seconds, 6/6 acuity with corrected refractive error) before and after a 20-minute exposure to stereoscopic viewing. During stimulation, vergence demand oscillated from 1 to 3 meter angles along a virtual sagittal line in sinusoidal movements, while accommodative demand was fixed at 1.5 diopters.
  
  
  
  Results showed a decreased CA/C ratio (-10.36%, df = 10, t = 2.835, P = 0.018), with no change in the AC/A ratio (P = 0.090), tonic vergence (P = 0.708), and tonic accommodation (P = 0.493).
  
  
  
  These findings demonstrated that the CA/C ratio can exhibit adaptive adjustments. The observed nature and amount of the oculomotor modification failed to compensate for the stereoscopic constraint.
authors.affiliation: Institut de recherche biomédicale des armées (IRBA), Action et cognition en situation opérationnelle, Brétigny-sur-Orge, France.
authors.forename: Pascaline
authors.initials: P
authors.lastname: Neveu
authors.affiliation: Institut de recherche biomédicale des armées (IRBA), Action et cognition en situation opérationnelle, Brétigny-sur-Orge, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Roumes
authors.affiliation: Institut de recherche biomédicale des armées (IRBA), Action et cognition en situation opérationnelle, Brétigny-sur-Orge, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Philippe
authors.affiliation: MinesParisTech, Centre de robotique, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Fuchs
authors.affiliation: Institut de recherche biomédicale des armées (IRBA), Action et cognition en situation opérationnelle, Brétigny-sur-Orge, France 3INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Center, Bron, France.
authors.forename: Anne-Emmanuelle
authors.initials: AE
authors.lastname: Priot
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D003290:Convergence, Ocular / Q000502:physiology*; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D009907:Optometry / Q000295:instrumentation; D012030:Refractive Errors / Q000503:physiopathology*; D015357:Vision Disparity / Q000502:physiology*; D014792:Visual Acuity; D055815:Young Adult