Vertical disconjugacy during reading in dyslexic and non-dyslexic children

Binocular coordination of children with dyslexia and typically developing children in linguistic and non-linguistic tasks: evidence from eye movements

Given the increased evidence suggesting the presence of binocular coordination deficits in dyslexia, investigations of binocular eye movements are beneficial to clarify the underlying causes of reading difficulties. This systematic review aims to (a) synthesize the literature through the examination of binocular coordination in children with dyslexia by describing the normative development of stable binocular control and (b) outline future directions. Boolean expressions in the PubMed search were used to define papers. Following a literature search and selection process, 25 papers were included. Studies using binocular eye tracking during linguistic and nonlinguistic tasks in children with dyslexia and typical development 5-17 years of age are reviewed. The studies reviewed provided consistent evidence of poor binocular coordination in children with dyslexia, but the results associated with different task characteristics were less consistent. The relation between binocular coordination deficits and reading difficulties needs to be further elucidated in longitudinal studies which may provide future treatments targeting the binocular viewing system in dyslexia.

Children with Dyslexia Have Altered Cross-Modal Processing Linked to Binocular Fusion. A Pilot Study

Introduction

The cause of dyslexia, a reading disability characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities, is unknown. A considerable body of evidence shows that dyslexics have phonological disorders. Other studies support a theory of altered cross-modal processing with the existence of a pan-sensory temporal processing deficit associated with dyslexia. Learning to read ultimately relies on the formation of automatic multisensory representations of sounds and their written representation while eyes fix a word or move along a text. We therefore studied the effect of brief sounds on vision with a modification of binocular fusion at the same time (using the Maddox Rod test).

Methods

To check if the effect of sound on vision is specific, we first tested with sounds and then replaced them with proprioceptive stimulation on 8 muscular sites. We tested two groups of children composed respectively of 14 dyslexic children and 10 controls.

Results

The results show transient visual scotoma (VS) produced by sensory stimulations associated with the manipulation of oculomotor balance, the effect being drastically higher in the dyslexic group. The spatial distribution of the VS is stochastic. The effect is not specific for sounds but exists also with proprioceptive stimulations.

Discussion

Although there was a very significant difference between the two groups, we were not able to correlate the (VS) occurrence with the dyslexic’s reading performance. One possibility to confirm the link between VS and reading impairment would be to find a specific treatment reducing the occurrence of the VS and to check its effect on dyslexia.

Are changes in the stomatognatic system able to modify the eye balance in dyslexia?

Objectives

To clarify the link between eye muscle function and oral information by comparing 21 dyslexic readers (DR) and 14 normal readers (NR).

Methods

Changes in vertical heterophoria (VH) were measured using the Maddox Rod Test performed according to oral modifications and postural conditions. The Spearman correlation was used to assess whether reading delay was correlated with the lability index.

Results

Overall, 50% of NR children and 81% of DR experienced at least one variation in visual perception (p = 0.053). Among DR, the less reading delay they had, the higher their index of lability (p = 0.026), whereas there was no significant correlation among NR. Changes in the Maddox Test were more frequent in DR than in NR after the addition of sensory and postural stimuli, except for one specific posture. For sensory stimuli, the mean lability index was 1.35 in NR and 4.19 in DR, (p = 0.001). For postural stimuli, it was 0.71 and 2.61, (p = 0.003).

Conclusions

It is possible to modify visual perception by changing sensory or mechanical stimuli. Changes are more frequent in DR than in NR. Postural control can be improved with guided oral stimulations.

Significance

These results reinforce the importance of professional cooperation in the care of dyslexic readers.