title: Evidence for frequent divergence impairment in French dyslexic children: deficit of convergence relaxation or of divergence per se?
abstract: OBJECTIVE
  There is a controversy as to whether dyslexic children present visuo-motor disabilities such as vergence and accommodative problems assessed with orthoptic tests. The purpose of this study is to re-examine this issue in a large population of children.
  
  
  METHODS
  Extensive orthoptic evaluation was made in 57 dyslexic and 46 non-dyslexic ("normal") age-matched children. Convergence and divergence capacities were evaluated at two distances (30 cm and 400 cm).
  
  
  RESULTS
  Binocular vision measured with stereo-acuity tests was normal in dyslexics. In contrast, the near point of convergence was significantly more remote in dyslexics; most importantly, divergence at both far and near distance was significantly more reduced in dyslexics (median value 4 pD and 10 pD, respectively, at far and near) than in "normals" (median value 6 pD and 12 pD, at far and near).
  
  
  CONCLUSIONS
  The existence of the divergence deficit at far distance indicates the presence of deficit of divergence per se, independently from convergence and accommodation relaxation. This result is novel and corroborated by physiological studies indicating distinct control of convergence and divergence, both at the cortical and subcortical premotor level. We conclude that vergence deficits are frequently present in dyslexics, and that dyslexics should be re-educated; training should address distinctively convergence and divergence subsystems.
authors.affiliation: IRIS Group/LPPA UMR 7152, CNRS-College de France, 11 place M. Berthelot, 75005 Paris, France. zoi.kapoula@college-de-france.fr
authors.forename: Zoï
authors.initials: Z
authors.lastname: Kapoula
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Bucci
authors.forename: Frederic
authors.initials: F
authors.lastname: Jurion
authors.forename: Julie
authors.initials: J
authors.lastname: Ayoun
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Afkhami
authors.forename: Dominique
authors.initials: D
authors.lastname: Brémond-Gignac
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology; D002648:Child; D003290:Convergence, Ocular / Q000502:physiology*; D004410:Dyslexia / Q000208:ethnology / Q000503:physiopathology*; D005099:Exotropia / Q000208:ethnology / Q000503:physiopathology*; D005602:France / Q000208:ethnology; D006801:Humans; D007361:Intelligence Tests; D009988:Orthoptics; D011932:Reading; D015348:Vision, Binocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology