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Reference: Riddell, Patricia Mary, (1987). Vergence eye movements and dyslexia. Dphil. University of Oxford.Citable link to this page:


Vergence eye movements and dyslexia

Abstract: Many theories have been proposed to explain why some otherwiseintelligent children have unexpected problems with learning to read.In this thesis, evidence is presented -in support of the hypothesisthat one cause of such children's difficulties is failure to developaccurate vergence eye movement control. This leads to impaired abilityto localise small targets reliably, thus explaining the 'visual'nature of some of these children's reading problems.In 432 dyslexic and normal children vergence eye movements wererecorded during the Dunlop Test of visual direction sense. Poorvergence eye movements were associated with variable ('unstable')responses in the Dunlop Test whilst good vergence control concordedwith stable Dunlop Test responses. Further analysis showed that manydyslexic children were significantly impaired in several measures ofvergence control when compared with either chronological or readingage matched controls. The parameters which distinguished most clearlybetween dyslexic and normal children's binocular control were found tobe a target 1 degree of angular subtense moving at 0.6 degrees/second.A computer game was also developed to measure the accuracy ofchildren's spatial localisation and to compare this with the resultsof the Dunlop Test. Children with unstable responses in the DunlopTest were significantly worse in this test than children with stableresponses. Overall, females were poorer at this test than males, withunstable females registering the lowest scores. A difference betweenthe percentage error rate in the left and right hemifields was alsoshown. Females with unstable Dunlop Test responses were poorer thanstable females in both visual fields, while unstable males made moreerrors than their stable counterparts only in the left visual field.These results provide confirmation of the hypothesis that females areless highly lateralised for visuospatial functions than males.A longitudinal study was carried out over 4 years on a cohort of 29primary school children. The children were found to improve in thestability of their Dunlop Test responses, the stability of theirvergence control and in their stereoacuity as they grew older. Thechildren with unstable Dunlop Test responses and poor vergence controlwere found be significantly worse readers than those who showed goodbinocular control. Also children who took longer to develop stableresponses to the Dunlop Test had poorer reading ability than those whodeveloped good binocular control at an early age.The results are discussed in relation to a model of the developmentof reading ability and other postulated causes of readingdifficulties. It is concluded that impaired vergence control may beassociated with unreliable spatial localisation of words and letters.This is thought to be a sufficient cause for the difficulties somechildren show when learning to read, though it may often appear incombination with impaired linguistic skills.

Type of Award:Dphil Level of Award:Doctoral Awarding Institution: University of Oxford Notes:The digital copy of this thesis has been made available thanks to the generosity of Dr Leonard Polonsky


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 Bibliographic Details

Issue Date: 1987Identifiers

Urn: uuid:fc695d53-073a-467d-bc8d-8d47c0b9321e

Source identifier: 603840749 Item Description

Type: Thesis;

Language: eng Subjects: Eye Movement disorders Movements Binocular vision Depth perception Dyslexia Tiny URL: td:603840749


Author: Riddell, Patricia Mary - institutionUniversity of Oxford facultyMedical Sciences Division facultyLaboratory of Physiology - - - -



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