Asymmetry of efferent signals to the iris muscles produces inequality in the diameters of the 2 pupils. This phenomenon, called anisocoria, may be physiologic or pathologic. Figure 10-1 shows an algorithm for evaluating a patient with isolated anisocoria. Specific disorders are discussed in the following sections.
Normal Pupillary Response to Light
When evaluating the pupils of a patient with anisocoria, the clinician should first check the pupillary light reflex (to determine whether the response to light is normal) and then evaluate whether the anisocoria is greater in dim or bright light. If the pupils react normally, the abnormality is of the sympathetic pathway. If one of the pupils responds abnormally to light, the next step is to examine the iris sphincter at the slit lamp to determine whether there are any secondary causes that explain the anisocoria.
Figure 10-1 Flowchart for evaluation of anisocoria. CN = cranial nerve.
(Based on an illustration by Helen Danesh-Meyer, MD.)
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.