Babies whose eyes react more strongly than normal to bright light have a higher risk of being diagnosed with autism than those whose eyes react normally to light, according to a study published in Nature Communications. Researchers from Uppsala University and the Center of Neurodevelopmental Disorders at Karolinska Institutet in Sweden state that this finding supports previous studies indicating that sensory processing plays a role in autism spectrum disorders.
Part of the Early Autism Sweden project, the study combined Swedish data with that of a similar study of infants with an older sibling who had autism conducted at the University of London. The researchers tested pupillary light reflexes, which control the amount of light that reaches the retina, in 147 babies, 9 or 10 months old, with an older sibling diagnosed who had been autism. A control group included 40 additional infants.
Normally, the pupils get smaller, or constrict, in response to bright light and widen, or dilate in low-light conditions. The researchers found that infants whose pupils constricted to a greater degree were more likely to meet the diagnostic criteria for autism at age 3, and that the amount of constriction was directly associated with the severity of the autism symptoms.