Latency of saccades and vergence eye movements in dyslexic children

Abstract

The goal of this study was to explore the latency of eye movements both in direction and in depth in dyslexic children. Sixteen dyslexic (mean age: 11.12 +/- 1.08 years) and 14 non-dyslexic children (mean age: 12.08 +/- 0.99 years) were tested. Two different paradigms (simultaneous and gap) were used to elicit pure saccades at far and at near distance, pure vergence (convergence and divergence) and combined saccade-vergence movements. Horizontal eye movements from both eyes were recorded simultaneously by a photoelectric device (Oculometer, Dr. Bouis). The mean latency of saccades at far distance (pure or combined) is significantly longer in dyslexics, regardless of the paradigm used. For both dyslexic and non-dyslexic children, latencies in the gap paradigm are shorter. Moreover, the occurrence of express latencies for divergence (pure or combined) is significantly higher for dyslexics. Difficulties in both voluntary and reflexive control shifts of visual attention from near to far distance in dyslexics could be at the origin of these findings.