Pupil is innervated by autonomic nerve system. As a result, its dimension or actions well reflects the autonomic nervous system
function. Pupillary autonomic neuropathy is considered an early symptom of the development of systemic autonomic neuropathy.
Pupil tests present suitable and easy methods for evaluation of autonomic nervous system function. Most patients with autonomic
nervous system disorders show data of sympathetic or parasympathetic deficits in the pupil, and these findings can be detected
using a combination of clinical signs, pupillometric and pharmacological tests.