Why do we shine lights in the eyes of conscious patients after head injury?

Pupil examination is a standard part of the neurological assessment of patients after head injury. The internationally recognised Advanced Trauma Life Support course teaches that Glasgow Coma Scale (GCS) score and pupillary responses should be assessed in all patients with head injuries.1 Similarly, the National Institute for Health and Care Excellence (NICE) recommends that, after initial assessment in the emergency department, a patient who is normally alert (with a GCS score of 15) after head injury should have their GCS and pupils assessed half hourly for two hours, then hourly for four hours, then two hourly thereafter.2

The rationale for pupillary assessment is that changes in pupil size and reaction can indicate a rise in intracranial pressure and can help to identify the location of …