Sex-specific lateralization of contraction anisocoria in transient pupillary light reflex.

PURPOSE Contraction anisocoria describes a phenomenon in which the pupil of a directly illuminated eye constricts more than the pupil of the consensual (not illuminated) eye. The purpose of this study was to investigate the lateralization of contraction anisocoria in young female and male subjects. METHODS Infrared binocular pupillography was used to measure pupillary light reflex (PLR) in 44 healthy children (23 girls, 21 boys) from 6 to 16 years of age. Measurements were conducted in both light-adapted and dark-adapted conditions with different stimulus intensities. Relative constriction amplitude was obtained by dividing the maximal pupil area change by the initial static pupil area. Contraction anisocoria was calculated by subtracting relative constriction amplitude in the consensual eye from that of the direct eye. Values of contraction anisocoria obtained by stimulating a subject's right or left eye were compared to determine any potential lateralization. RESULTS It was found that stimulating the right eye led to larger contraction anisocoria than stimulating the left eye. Such right-side lateralization of contraction anisocoria is much greater in males than in females. In addition, the effects of sex were related to the ambient light level and stimulus intensity. CONCLUSIONS These results provide evidence that contraction anisocoria is more laterally asymmetric in males than in females.