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The Prevalence of Physiological Anisocoria and its Clinical Significance - A Neurosurgical Perspective

Aim: We aimed to estimate the prevalence of physiological anisocoria and also evaluate the accuracy of clinical assessment of anisocoria employed in routine bedside examination. Materials and Methods: A total of 708 voluntary subjects between the ages of 20–69 years who had no history of ophthalmologic or neurological disease other than refractive error were included in the study. In a closed room with uniform ambient lighting, the subjects' pupils were examined clinically and the presence or absence of anisocoria was recorded. This was followed by photography of the subjects' pupils using a digital camera secured on a tripod at a fixed distance from the subject's face. A difference in pupillary size of 0.4 mm or more was considered anisocoria. Results: Of the 708 subjects, 361 (51%) were males. The average pupillary diameter of the subjects was 4.99 mm. Ninety-seven (13.7%) had measured anisocoria on photography. Ninety-seven subjects (13.7%) also had anisocoria on clinical examination, however, only 45 of them had measured anisocoria. The clinical measurement of anisocoria, therefore, showed a specificity of 0.91 and a sensitivity of 0.46. With a prevalence of anisocoria of 13.7%, the positive predictive value was 0.46, and the negative predictive value was 0.91. Conclusions: The prevalence of physiological anisocoria was 13.7%, which is less than what has previously been reported. The sensitivity of clinical examination in detecting early anisocoria is poor. Patients at risk of developing uncal herniation may, therefore, benefit from routine bedside pupillary assessment with a portable device such as a pupillometer.