Benign alternating anisocoria

Abstract

Aims: To characterise and compare the variability of anisocoria measurements in normal healthy subjects and patients with alternating anisocoria. Methods: Using flash photography or infra-red pupillometry, serial measurements of pupil diameter were made in two patients presenting with alternating anisocoria, both daughters of Patient 2, and eight normal subjects. In each individual the distribution of anisocoria measurements was compared with a Gaussian normal distribution using a Chi-squared test. Results: The distribution of anisocoria measurements was Gaussian in all control subjects but bimodal in both patients. The elder daughter of Patient 2 showed a bimodal distribution which weakly departed from normality (p = 0.101) and her younger sister showed a unimodal distribution. In all cases the pupils reacted normally to a light stimulus or an accommodative effort; visual function, and ocular and neurological examination were normal. Conclusion: Alternating anisocoria is a discreet entity not found in normal subjects but which may be present in more than one member of a family. Because it occurs in otherwise healthy individuals, we recommend it should be called benign alternating anisocoria. The neural mechanism underlying this phenomenon remains unclear.

• Pupil
• Anisocoria
• Familial
• Edinger-Westphal Nuclei