Definition of Anisocoria in Neurocritical Patients

INTRODUCTION: Anisocoria, defined as the absolute difference in left and right pupil diameter, is an important clinical finding. However, the definition of anisocoria varies and clinicians have limited reliability in estimating pupil size through subjective measurements. Using a quantitative pupillometer (QP) increases the accuracy and consistency in pupil measurement.

OBJECTIVES: The primary objective of this study is to examine the presence of anisocoria at rest, and anisocoria after exposure to light, using QP in a cohort of Neuroscience intensive care unit (NSICU) patients. The secondary objective is to explore anisocoria using different cutpoints for differences in size.

MATERIALS & METHODS: Retrospective analysis from an international registry was queried to obtain the first paired QP measurement from patients admitted to one of 4 US and 2 international NSICUs.

DISCUSSION/RESULTS: Sample size includes 5769 patients with a mean age of 57.5 (17.6%) years. Of these, 2,558 (51.5%) were female, 3,669 (75.5%) were White, and 4,369 (89.2%) were non-Hispanic. Hospital length of stay was a median of 6 (3 to 14) days, and the median ICU length of stay was (1 to 8) days. Using the smallest cutpoint of > 0.5 mm, anisocoria was present at rest in 1,642 (28.2%) and after light stimulus in 885 (15.3%) observations (P<.0001). Using the largest cut-point of > 2.0 mm anisocoria was present at rest in 79 (1.4%) of our sample and after light stimulus in 74 (1.3%) observations (P<.0001).

SUMMARY/CONCLUSION: There is a statistically significant difference in anisocoria before and after exposing the pupil to light. This difference persists across anisocoria cutpoints ranging from 0.5 to 2.0mm. Future study should examine anisocoria before and after light exposure for association with radiological or clinical findings.