Late Light-Off Pupil Response Predicts Consciousness Gains Seven Days Later in 250-Patient ICU Cohort

Researchers at Rigshospitalet and DTU performed daily automated pupillometry in patients with traumatic and anoxic injury. The late light-off response (LOR) was measured after the initial constriction phase using existing handheld devices; each test lasted 13 seconds. LOR latency remained associated with recovery after adjustment for sedation, baseline Glasgow Coma Scale, and injury mechanism, yet showed no same-day correlation with responsiveness, suggesting it captures latent circuit recovery rather than current arousal.

Existing pupillometry metrics focus on brainstem reflex arcs that are already impaired at presentation. LOR may index slower thalamocortical or cholinergic modulation that precedes behavioral improvement. The signal was strongest in unsedated anoxic cases, but these strata were small and exploratory. No data were reported on long-term functional outcome or interrater reliability outside the research team.

Prior observational cohorts using EEG and fMRI have shown similar delayed prognostic signals, yet none have been integrated into routine 13-second bedside workflows. If replicated, LOR could stratify patients for early rehabilitation trials before overt signs emerge. The next required step is a multicenter prospective validation with pre-registered endpoints and blinded outcome assessment at 90 days.