Pupillary light reflex in children with autism spectrum disorders

Abstract

Pupillary light reflex (PLR) refers to the phenomenon of pupil size changing with respect to retinal illumination. It's a noninvasive, functional test which can reveal a rich set of information about nervous system. Abnormal PLR in children with autism spectrum disorders (ASD) was previously reported in a small population. In this research, a series of systematic studies were carried out to investigate the association of atypical PLR with ASD in a large population. An experimental protocol was developed to measure PLR simultaneously with heart rate variability (HRV), a commonly used autonomic nervous system (ANS) measure. Our results indicate that variations of PLR and HRV are not associated in typically developing children. However, significant age effects on both PLR and HRV were observed in this population. In typically developing children, the resting pupil diameter increased with age significantly up to age 12. PLR constriction increased with age in children younger than 8 years old and reached a plateau thereafter. PLR latency decreased significantly from 6 to 9 years and stabilized thereafter. The average heart rate (AHR) decreased with age in typically developing children. Standard deviation of normal-to-normal intervals (SDNN) showed little change before 12 years of age but was increased in older children. High frequency normalized power (HFN) decreased with age in typically developing (TD) group. PLR and HRV were also measured in 152 children with ASD and 36 children with non-ASD neurodevelopmental disorders (NDDs). The results showed atypical PLR in the ASD group including longer PLR latency, reduced relative constriction amplitude, and shorter constriction/redilation time. Similar atypical PLR parameters were observed in the NDD group. The ASD and NDD groups had faster AHR than the TD group. The NDD group also showed a significantly faster AHR than the ASD group. The age effect on PLR latency which was observed in typically developing children of 6-9 years old was not observed in the ASD and NDD grou