A test of the oculocephalic reflex that can be used to assess the integrity of the brainstem in neonates and comatose patients. During the evaluation of the comatose patient, with the patient’s eyes held open, the head is quickly rotated from one side to the other. Both eyes should deviate to the side opposite the direction of head rotation. If this response is absent, there may be damage to the brainstem or oculomotor nerves. By contrast, in the evaluation of the newborn (whose nervous system is immature), the irises normally remain in midline despite the rotation of the head.