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  • Updated 02.13.2020
  • Released 08.28.1998
  • Expires For CME 02.13.2023

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: objective, helpful, and difficult to fake. 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 “no fail” pupil examination includes: (1) afferent: the swinging flashlight test to determine the presence of a relative afferent pupillary defect; and (2) efferent: measurement of the pupil size in the light and in the dark to assess for anisocoria; and light-near dissociation: assessment of the pupillary light reaction in each eye, and if sluggish, measure the near response for assessment of light near dissociation.

• Parasympathetic pupils: Adie tonic pupil and oculomotor palsy pupil look the same but may be distinguished by the company they keep. Consider diplopia and a ptosis an oculomotor palsy and light-near dissociation with vermiform movements of the iris sphincter an Adie pupil.

• Sympathetic pupils: apraclonidine is useful for pharmacologic testing of a suspected Horner syndrome and, unlike cocaine drops, is commercially available.

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 2 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 (53).

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