Binocular Coordination of Saccades in 7 Years Old Children in Single Word Reading and Target Fixation

The purpose of the present study was to examine in 7 years old normal children who just learnt to read, saccade and fixation characteristics during reading single words. Eight children were studied and their results were compared to those of eight normal adults doing the same task. For each group word reading data were also compared with data in a task requiring saccades and fixations to target-LEDs. Horizontal saccades from both eyes were recorded with a photoelectric device (Oculometer, Bouis). Latencies of saccades both to words and to LEDs presented at predictable location were similar, and they were also similar between children and adults. In contrast, disconjugacy of saccades was significantly increased for children and similar in the two tasks (LEDs or words). Disconjugate post-saccadic drift and its velocity were also significantly higher in children and similar in the two tasks. Substantial conjugate leftward drift was present for children only, and for the word task only. Finally, fixation duration on words was significantly longer in children than in adults. We conclude that binocular coordination and fixation stability is poor in children and that it could be partially responsible for the long fixation duration. Binocular coordination does not depend on the task (LEDs or words) neither for adults, nor for children; this contrasts prior reports.