The pupillary examination.

Abstract

Introduction Many pupil abnormalities, including irregularities of shape or position, anisocoria (difference in pupil size) and abnormalities of the light and/or near response, may be seen in hospital. Although many of these pupil abnormalities are asymptomatic, changes to the pupils may be a sign of underlying ophthalmic or neurological disease. A thoughtful and detailed pupillary assessment, alongside a thorough history and neurological examination, will reward the doctor with clues to many diagnoses. The detail with which the pupils are examined varies depending on the clinical scenario. This article first reviews relevant anatomy and salient aspects of the examination, then divides pupillary findings into practical categories to enable junior doctors to make a confident clinical diagnosis. Emphasis is placed on neurological causes of pupillary abnormalities, although if signs do not fit with a ‘neurological’ cause, an ophthalmic opinion should be sought. The neuroanatomy A working knowledge of the anatomy of the light reflex and sympathetic innervation is key to taking the diagnostic leap from a simple description of pupillary findings to meaningful interpretation of these clinical signs. Pupil size is controlled by the interplay between parasympathetic innervated smooth muscle constrictors and sympathetic innervated dilators of the iris. The anatomical separation of these two nerve chains helps in lesion localization.