Eye-tracker-based evaluation of saccadic deficits in young children with developmental disorders

Abstract

Visually guided saccadic eye movement has been considered a promising screening tool for cognitive function because of its simple and objective nature. However, its application to young children, especially those with developmental disorders, is limited due to the lack of sustained attention required to complete the measurement using the traditional electrophysiological protocol. We have previously reported that saccades can be reliably evaluated in typically developing young children using an eye tracker, which allows non-contact measurement of eye movement with a sufficiently short preparation time. Using the eye tracker system combined with an in-house developed analysis software, we investigated the changes in saccadic behavior between typically developing children (n = 30) and children with developmental disorders (attention-deficit/hyperactivity disorder [ADHD] and autism spectrum disorder [ASD], n = 27) at ages ranging from 4.8 to13.2 years. Four saccade responses were measured, consisting of eye movement to the instantaneously shifted visual target either to the right or left (step condition), to the visual target that appeared 200 ms after turning off the fixation point (gap condition), to the visual target while the fixation point remained (overlap condition), and in the direction opposite to the visual target (anti-saccade condition). Statistically significant deficits were found in children with developmental disorders compared to typically developing children, with decreased number of correct saccades in the step condition in children with ASD and reduced peak saccadic velocity in the overlap condition in children with ADHD. Interestingly, when saccadic parameters were further evaluated with regard to the direction of eye movement (rightward and leftward), a significant decrease in peak velocity in children with developmental disorders compared to typically developing children was only confirmed in saccades to the right side in the overlap condition. In addition, right-lateralized deficits in peak velocity and initial accuracy were also found in the step, overlap, and anti-saccade conditions in children with developmental disorders. These lateralized oculomotor responses may represent the affected cortical function in children with developmental disorders, suggesting a possible role of non-contact saccadic examination as an assessment tool for visual cognitive function, especially in young children.