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Autism diagnosis linked to light response in infants

Research by Birkbeck and Uppsala University, Sweden, shows a strong pupil response to light could be an early marker of autism spectrum disorder (ASD).

A new study conducted at Uppsala University, Karolinska Institute (Sweden) and Birkbeck shows that infants who react more strongly to sudden changes in light intensity are more likely to later be diagnosed with autism spectrum disorder.

This finding provides support for the view that sensory processing plays an important role in the development of this condition. The study is published in the journal Nature Communications.

Researchers investigated the pupillary light reflex - a basic mechanism controlling the amount of light that reaches the retina in which the pupil contracts when the eye is exposed to sudden increases in brightness - in young children in Sweden and the UK.

In this study, an eye-tracker was used to measure these changes in pupil size. The participants were 10 months old when their pupillary responses to light were first examined and 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 associated with the strength of autism symptoms at three years old.

Dr Teodora Gliga, Research Fellow from 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 reside 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.”

“We believe the findings are important because they point to a very basic function that has not been studied before in human infants,” says Terje Falck-Ytter, Associate Professor at the Department of Psychology, Uppsala University and Principal Investigator for the study.

Across the two countries, the study looked at 147 infants with an older sibling with ASD enrolled in the study. Of these, 29 met the criteria for ASD at the follow-up. The study also included a control group of 40 typically developing infants from the general population.

Dr Gliga said: “A large sample is needed to reach the statistical power that can give us confidence in the findings. This was made possible by the ongoing collaboration within the Euro-sibs, a European network for the study of the developmental origins of autism.”

The study was conducted in collaboration between the Early Autism Sweden (EASE), conducted at Uppsala University and the Center of Neurodevelopmental Disorders at Karolinska Institutet (Sweden) and the British Autism Study for Infant Siblings (BASIS), conducted at the Centre for Brain and Cognitive Development, Birkbeck, University of London (UK).

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