Abstract:

Perception disorders, especially those of vision, in individuals with autism spectrum disorder (ASD) have a significant diagnostic value. Earlier studies have shown that both adults and children with ASD have vision disorders, like double vision, strabismus, amblyopia, etc., which may cause difficulties in processing visual information. Smooth pursuit eye movement (SPEM) can be used to research perception and processing of motion information that track the target’s movement. Failure of visual processing of motion stimuli in individuals with ASD was reported in several earlier studies. There is little existing knowledge about the mechanism underlying the failure to effectively perform visual tracking in individuals with ASD. Given the visual problems of these individuals, we supposed that dysfunction of binocular fusion affects the ability to track targets precisely. Distance between the external fixation points corresponding to the object image on the retina, that is, the distance of the binocular point of regard (DBPR) is abnormal in ASD. Some studies reported that irrespective of static or dynamic stimuli, the DBPR in children with ASD is significantly greater than that of typically developing (TD) children. Therefore, we investigated the visual mechanism and identification value of the DBPR in children with ASD, using a smooth-tracking task.

We designed a study to test the visual mechanism and identification value of the DBPR in children with ASD during dynamic stimulation processing. We recruited 25 children with ASD, aged 3 to 6 years, and 25 TD children of corresponding age, who were made to watch 6 smooth-tracking task videos of sinusoidal motion of a small black sphere, which were recorded along with the original coordinates of binocular vision through an eye tracker. We compared differences in TD children and those with ASD, by calculating the position error and DBPR in 6 conditions.

The results showed that: (1) the DBPR in children with ASD is abnormal, and is independent of strabismus, (2) compared with TD children, whose average DBPR value is less than 30 pixels, the DBPR in children with ASD is higher. Average DBPR value in children with ASD is greater than 35 pixels and has cross-task stability, (3) the DBPR in children with ASD has good identification ability in all six conditions, especially under the conditions of highest amplitude and speed, and (4) the DBPR is significantly positively correlated with gross score of the autism behavior checklist (ABC) and dimension of sensation, showing that it can be used as an identification index to measure abnormal perception in children with ASD.

In conclusion, compared with TD children, the DBPR in those with ASD reflects the defect of binocular vision and has cross-task stability. It has good identification value under the conditions of fastest speed and highest amplitude.

Key words: autism spectrum disorder, smooth tracking, distance of the binocular point of regard.