A new study suggests that pupillary response to light stimuli may be a fast and objective physiologic biomarker for adolescent sport concussion. Currently, concussion diagnosis is clinical and there aren’t any objective diagnostic tests for adolescents. Pupillary light reflex shows promise because reduced visual accommodation and autonomic function often accompany concussion.

The prospective cohort study included athletes between the ages of 12 and 18 with sports-related concussion (n=98) from a specialty concussion program and healthy controls (n=134) from a private suburban high school. The researchers recorded pupillary light reflex metrics a median of 12 days after the injury. These included minimum and maximum pupil diameter, percentage of constriction, average and peak constriction and dilation velocity and time to 75% pupillary redilation.

The team found that athletes with concussion exhibited significantly greater pupillary reflex metrics. They also observed that girls with concussion exhibited longer time to 75% pupillary redilation (1.96 seconds vs. 1.63 seconds). Healthy controls had diminished pupillary reflex metrics (e.g., smaller maximum pupil size) after exercise.

They concluded that enhanced pupillary reflex is a characteristic of acute adolescent concussion, while an overall slowing of reflex and small pupil sizes tends to follow exercise (likely associated with fatigue). They believe that the quantifiable measures of pupillary reflex can serve as objective physiologic biomarkers for sports-related concussion in adolescents.