
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.

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.A “low tech” algorithm leads the clinician through the evaluation process to know whether the patient can be reassured or needs additional testing.

The author discusses causes of anisocoria and abnormal pupillary activity. 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.
