Baby's pupils that react to light changes could mean they will later be diagnosed with autism.
A study has shown that babies whose pupils react more strongly to sudden light changes are more likely to be diagnosed with autism spectrum disorder in later life.
Researchers at Birbeck, University of London, said it provides support for the view that sensory processing plays an important role in the development of the disorder.
The findings, published in Nature Communications Journal, could eventually lead to improvements in early detection of autism.
The participants, from the UK and Sweden, were 10 months old when their pupillary responses to light were first examined with an eye-tracker that measured these changes in pupil size.
They were followed until they were three years of age, at which point they took part in a diagnostic evaluation.
Those infants who eventually fulfilled criteria for ASD showed a stronger pupillary response than infants who did not later fulfil ASD criteria.
The amount of pupil constriction in infancy was also associated with the strength of autism symptoms at three years old.
Across the two countries, the study looked at 147 infants with an older sibling with ASD.Of these, 29 met the criteria for ASD at the follow-up. The study also included a control group of 40 typically developing infants.
Dr Teodora Gliga, a research fellow at Birkbeck's Centre for Brain and Cognitive Development, who led the UK branch of the study, said: "For a long time, autism has been defined by atypical social interaction and communication.
"However, researchers are increasingly embracing the view that the earliest signs of the condition may lie in more basic processes of brain development.
"Understanding the developmental mechanisms behind autism will help improve early detection as well as the design of early interventions."
The research was carried out in conjunction with Sweden's Uppsala University.
Autism spectrum disorder (ASD) is the name for a range of similar conditions, including Asperger syndrome, that affect a person's social interaction, communication, interests and behaviour. In children with ASD, the symptoms are present before three years of age, although a diagnosis can sometimes be made after the age of three.
It's estimated that about 1 in every 100 people in the UK has ASD. More boys are diagnosed with the condition than girls.
Written by Lucy Hollis.
9 stunning locations in the UK which are inspired by children’s books
Like this? You might also be interested in: