Approach to pupillary abnormalities via anatomical pathways

Abstract

The pupillary size and movement are controlled dynamically by the autonomic nervous system; the parasym-pathetic system constricts the iris, while the sympathetic system dilates the iris. Under normal conditions, these constrictions and dilations occur identically in both eyes. Asymmetry in the pupillomotor neural input or output leads to impaired pupillary movement on one side and an unequal pupil size between both eyes. Anisocoria is one of the most common signs in neuro-ophthalmology, and the neurological disorders that frequently cause anisocoria include serious diseases, such as vascular dissection, fistula, and aneurysm. A careful history and examination can identify and localize pupillary disorders and provide a guide for appro-priate evaluations.