In general, autism is a developmental disorder primarily impacting communication and behavior, and symptoms usually occur in the first two years of a child’s life.
"Earlier studies on older children with autism has suggested a weak pupillary light reflex in this group,” explained principal investigator Terje Falck-Ytter from Uppsala University. “These findings motivated us to assess the reflex in infant siblings of children with autism.”
However, in the new study researchers observed the opposite relationship between the pupillary light reflex and diagnosis with autism.
The pupillary light reflex is the pupil’s response to changing light conditions. By contracting or dilating, the pupil regulates the amount of light that reaches the retina. This reflex allows the pupils to react together or consensually, and it occurs even when a person is unconscious.
The study involved evaluating the pupillary light reflex in 147 9-to-10 month-old infants. For those infants who would later be diagnosed with autism at three years old, researchers saw more pupil constriction in response to changing light conditions than infants who were not diagnosed with autism. According to results from a follow-up after three years, the amount of pupil constriction in infancy was associated with autism severity.
"We believe the findings are important because they point to a very basic function that has not been studied before in infants with later autism diagnosis,” Falck-Ytter said.
A 2018 Centers for Disease Control and Prevention (CDC) surveillance study showed that one in 59 children are diagnosed with autism spectrum disorder (ASD). More boys (one in 37) are affected than girls (one in 151).
"Currently, autism cannot be reliably diagnosed before 2-3 years of age, but we hope that with more knowledge about the early development of the condition, reliable diagnosis will be possible earlier, which should facilitate early access to intervention and support for the families,” Falck-Ytter concluded. “New knowledge about early development in autism may also provide new leads on strategies for early intervention.”
The present study was published in the journal Nature Communications.