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  • Updated 06.13.2023
  • Released 08.28.1998
  • Expires For CME 06.13.2026

Pupillary abnormalities



Does the patient have an aneurysm or is it just physiologic anisocoria? The pupil exam is to the eye what the deep tendon reflexes are to the neurologic exam: an objective and easily elicitable measurement. The author discusses causes of anisocoria and abnormal pupillary activity. A “low tech” algorithm leads the clinician through the evaluation process to know whether the patient can be reassured or needs additional testing.

Key points

• The pupil examination includes: (1) swinging flashlight test to determine the presence of a relative afferent pupillary defect; and (2) measurement of pupil size in dim illumination and constriction to light and a near target.

• The mydriatic pupil of oculomotor palsy must be distinguished from “isolated” pupil disturbances, including tonic (Adie) pupil and pharmacologic and traumatic (including post intraocular surgery) mydriasis.

• The miotic pupil of Horner syndrome should be recognized and confirmed with topical apraclonidine testing.

Historical note and terminology

Around 200 A.D., Galen likened the iris to an elastic circular ring that was passively inflated or deflated by vital spirits sent from the brain to enhance vision. It was not until the first half of the 18th century that it became widely accepted that iris movement and pupil size were due to active interaction of two iris muscles: a longitudinal radial dilator and a circular sphincter muscle.

Many contributions to our understanding of pupillary physiology and pathology were made in the 20th century, including the description of the swinging flashlight test for assessing a relative afferent pupillary defect (47).

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