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Poor binocular coordination of saccades in dyslexic children
Maria Pia Bucci1, Dominique Brémond-Gignac, Zoï Kapoula
1IRIS Group, CNRS, Service OPH-ORL-Stomatologie, Hôpital Européen Georges Pompidou & Pôle Chirurgie ORL-OPH, Hôpital Robert Debré, Paris, France. mariapia.bucci@gmail.com
Insights
Children with dyslexia exhibit poorer binocular coordination during saccades, indicating an intrinsic ocular motor deficiency potentially linked to immature learning mechanisms for eye movement control.
Area of Science:
- Neuroscience
- Ophthalmology
- Developmental Psychology
Background:
- Dyslexia is a neurodevelopmental disorder affecting reading.
- Ocular motor control plays a role in reading fluency.
- Binocular coordination is essential for stable visual perception.
Purpose of the Study:
- To investigate the quality of binocular coordination of saccades in dyslexic children.
- To compare saccade coordination during single-word reading and fixation tasks.
- To identify potential ocular motor deficiencies in dyslexia.
Main Methods:
- Studied 18 children with dyslexia and 13 non-dyslexic controls.
- Recorded horizontal saccades from both eyes using a photoelectric system.
- Assessed binocular coordination during reading and fixation tasks.
Main Results:
- Dyslexic children showed worse binocular coordination during and after saccades compared to controls.
- This disconjugacy was consistent across different tasks.
- Dyslexics lacked the typical divergence-convergence pattern and exhibited larger post-saccadic drift.
Conclusions:
- Poor saccade coordination and eye drift suggest an intrinsic ocular motor deficiency in dyslexia.
- This deficiency may stem from immature ocular motor learning mechanisms.
- Cerebellar and cortical areas (parietal cortex) may be involved in this impaired learning.
Aim:
To examine the quality of binocular coordination of saccades in dyslexic children in single word reading and in a task requiring fixation of single LED.
Methods:
Eighteen children with dyslexia (11.4 +/- 2 years old) and 13 non-dyslexic children of matched age were studied. Horizontal saccades from both eyes were recorded with a photoelectric system (Oculomotor-Bouis).
Results:
Binocular coordination during and after the saccade in dyslexics is worse than that of non-dyslexic children; the disconjugacy does not depend on the condition. Moreover, dyslexics do not show the stereotyped pattern of disconjugacy (divergence during the saccade and convergence after the saccade). The conjugate post-saccadic drift is larger in dyslexics for both conditions.
Conclusion:
Poor quality of binocular coordination of saccades and drift of the eyes after the saccade, regardless of the task, indicates an intrinsic ocular motor deficiency. Such a deficiency could be related to immaturity of the normal ocular motor learning mechanisms via which ocular motor coordination and stable fixation are achieved. Learning could be based on the interaction between the saccade and vergence subsystems. The cerebellum, but also cortical areas of the magnocellular stream such as the parietal cortex, could be the sites of ocular motor learning.
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