In the new study, the researchers investigated the pupillary light reflex in 9-to-10 month old infants -- this reflex is a basic regulatory mechanism controlling the amount of light that reaches the retina. The infants who fulfilled criteria for autism at three years of age constricted their pupils more than infants who did not fulfill autism criteria at follow up. Further, the amount of pupil restriction in infancy was associated with the strength of autism symptoms at follow up.
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