Evidence for frequent divergence impairment in French dyslexic children: deficit of convergence relaxation or of divergence per se? |
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Authors: | Zoï Kapoula Maria Pia Bucci Frederic Jurion Julie Ayoun Farzaneh Afkhami Dominique Brémond-Gignac |
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Institution: | 1. IRIS Group/LPPA UMR 7152, CNRS–College de France, 11 place M. Berthelot, 75005, Paris, France 2. H?pital Robert Debré, service d’ophtalmologie, Paris, France
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Abstract: | Aim 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).
Conclusion 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. |
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Keywords: | Dyslexia Children Convergence Divergence Visual training |
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