Immaturity of the oculomotor saccade and vergence interaction in dyslexic children: evidence from a reading and visual search study

Maria Pia Bucci, Naziha Nassibi, Christophe-Loic Gerard, Emmanuel Bui-Quoc, Magali Seassau, Maria Pia Bucci, Naziha Nassibi, Christophe-Loic Gerard, Emmanuel Bui-Quoc, Magali Seassau

Abstract

Studies comparing binocular eye movements during reading and visual search in dyslexic children are, at our knowledge, inexistent. In the present study we examined ocular motor characteristics in dyslexic children versus two groups of non dyslexic children with chronological/reading age-matched. Binocular eye movements were recorded by an infrared system (mobileEBT®, e(ye)BRAIN) in twelve dyslexic children (mean age 11 years old) and a group of chronological age-matched (N = 9) and reading age-matched (N = 10) non dyslexic children. Two visual tasks were used: text reading and visual search. Independently of the task, the ocular motor behavior in dyslexic children is similar to those reported in reading age-matched non dyslexic children: many and longer fixations as well as poor quality of binocular coordination during and after the saccades. In contrast, chronological age-matched non dyslexic children showed a small number of fixations and short duration of fixations in reading task with respect to visual search task; furthermore their saccades were well yoked in both tasks. The atypical eye movement's patterns observed in dyslexic children suggest a deficiency in the visual attentional processing as well as an immaturity of the ocular motor saccade and vergence systems interaction.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Oculomotor paradigms.
Figure 1. Oculomotor paradigms.
Reading (A and B) and visual search (C and D) task respectively used for children with reading age of 7–9 and 10–12 years, respectively.
Figure 2. Eye movement pattern during reading…
Figure 2. Eye movement pattern during reading and visual search.
Number and duration of fixations from dominant right eye the in x- and y-coordinates from a dyslexic child (11 years old) from a non dyslexic child (9 years old) and from a non dyslexic child (11 years old).
Figure 3. Fixation duration ata.
Figure 3. Fixation duration ata.
Mean values of fixation duration (in ms) during reading and during visual search for the three groups of children tested. Vertical lines indicate the standard error.
Figure 4. Amplitude of saccades.
Figure 4. Amplitude of saccades.
Mean values of amplitude of saccades (in deg) during reading and during visual search for the three groups of children tested. Vertical lines indicate the standard error.
Figure 5. Disconjugacy during and after the…
Figure 5. Disconjugacy during and after the saccades.
Mean values of disconjugacy (measured as the percentage of ratio of the disconjugacy on the saccade amplitude) during (A) and after (B) the saccades during reading and during visual search for the three groups of children tested. Vertical lines indicate the standard error.

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Source: PubMed

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