From outer space to earth: Ultrasonographic dynamic pupillometry for autonomic testing and neuro-critical care

The assessment of pupil diameter as well as its response to light (pupillary light reflex) and to cutaneous painful stimuli (ciliospinal reflex) is a clinical standard in the evaluation of basic functions of the brainstem, cranial nerves, and the autonomic nervous system. In patients with traumatic brain injury or hypoxic ischemic encephalopathy, testing for the presence versus absence of pupillary reflexes is of high prognostic value already in the first hours after injury [1] [2]. Classically, pupillary responses to stimuli are assessed visually by the responsible physician or nurse. Meanwhile, there are a number of instruments available that allow for quantitative dynamic pupillometry by continuous infrared camera, normal-light eye tracker, or smartphone app-tracked, video recording of pupil diameter in the first seconds or minutes following an external or internal stimulus [3] [4] [5] [6]. Based on the recorded diameter-time function, indices of parasympathetic pupil innervation (constriction amplitude and velocity) and of sympathetic pupil function (dilation amplitude and velocity) can be calculated. Beside applications in neuro-critical care and anesthesiology, such as the prognostication after brain injury and the monitoring of anesthesia [5] [7], dynamic pupillometry allows the separate quantification of sympathetic and parasympathic autonomic function, e. g. for the discrimination of Parkinsonian disorders [3] [8] [9].

Publication History

Article published online:
02 February 2021

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