In indirect light reflex testing, the normal response is that the contralateral pupil constricts.

• A. Normal: contralateral pupil constricts
• B. Normal: ipsilateral pupil constricts
• C. Normal: both pupils dilate
• D. Normal: no pupil change

Answer: (A)

Indirect light reflex relies on a consensual response: shining light into one eye should trigger constriction in both pupils, and the pupil opposite the stimulated eye is the one used to assess this reflex. In a normal result, the contralateral pupil constricts because the retinal input from the stimulated eye signals the brain to activate both Edinger-Westphal nuclei, sending parasympathetic signals through both oculomotor nerves to constrict both irises. This demonstrates an intact reflex pathway on the side opposite the light. If the opposite pupil fails to constrict, that suggests a disruption in the afferent signal from the stimulated eye or an efferent defect affecting that side, whereas a direct constriction of the stimulated eye alone, dilation, or no change would point to different abnormalities.