A vestibular caloric test or caloric reflex test tests the reflex that allows the eyes to remain focussed on a subject by having the eyes automatically move in the opposite direction that the head moves. It involves irrigating the outer canal of the ear (between the eardrum and the opening of the ear) with either cold or warm water using a syringe. Because this is a test of a reflex, it will even work on patients in a coma. If the eyes do not move, it usually indicates damage to the brain stem and a poor prognosis.