Association Between Sensory Behavior and Pupillary Light Reflex in Children with Autism Spectrum Disorders

Background:  Atypical pupillary light reflexes (PLR) have been observed in children with autism spectrum disorders (ASD), suggests potential autonomic nervous system (ANS) dysfunction in ASD. ANS is also involved in modulating sensory processing and sensory processing problems are widely reported in children with ASD. However, the potential correlations between physical measurements (e.g. PLR) and behavioral observations (e.g. sensory) have rarely been examined in literature.

Objectives:   To study the association between sensory behavior and PLR parameters in children with ASD. 

Methods:  We examined PLR in 259 children including 152 with ASD (age 10.7±3.4 years) and 107 with typical development (TD) (age 10.9 ± 2.9 years). The test was conducted in both light adapted (LA) and dark adapted (DA) conditions using a two channel binocular apparatus. To quantify PLR responses, five basic PLR parameters were extracted including resting pupil diameter, relative constriction amplitude, latency, constriction velocity and redilation velocity.  The parent or guardian completed a 29-item questionnaire adapted from Dunn (1994) designed to evaluate sensory behavior. Linear correlations were first applied to analyze the association between PLR parameters and sensory total score. Linear regression was then used to investigate whether variations in PLR parameters can be explained by a combination of sensory behaviors. The partial least squares (PLS) regression was performed to select a subset of sensory behaviors as predictor variables that can explain the maximum variance in PLR parameters.

Results:  PLR constriction amplitude correlated with the sensory total score (r ≈ 0.3, p < 0.02) in the ASD group but not in the typically developing group (p > 0.05). No correlation was found between sensory total score and other PLR parameters. PLR constriction amplitude obtained in the ASD group at the highest stimulus intensity in light adaptation was best predicted in our regression analysis using the sensory item “Avoids getting messy” (b = 1.4 p=0.017) and “Has difficulty paying attention” (b =1.8 p=0.005). Post-hoc one-way ANOVA revealed significant effects from items “Avoids getting messy” (F=4.93 p=0.028) and “Has difficulty paying attention” (F=7.05 p=0.0088) on PLR constriction amplitude in the ASD group. Children with ASD who reported “rarely” or “never” on the aforementioned two items had greater PLR constriction amplitude than those who reported “always”. In the PLS regression model, the above two items plus 7 others were selected and can explain 11.1% of the data variance in PLR constriction amplitude.

Conclusions: A weak but significant correlation existed between PLR constriction amplitude and sensory total score in the ASD group but not in typically developing children. Lower PLR constriction amplitude suggests lower parasympathetic modulation. This observation implied that the abnormal sensory behavior in children with ASD could be associated with lower parasympathetic modulation.