Final answer:
The consensual pupillary reflex assesses the integrity of the oculomotor nerve (CN III) by observing the pupillary constriction in both eyes when light is directed into one eye.
Step-by-step explanation:
The consensual pupillary reflex assesses the integrity of the oculomotor nerve (CN III). This reflex involves sensory input received through the optic nerve (CN II), with a motor response mediated by the oculomotor nerve. If light shined in one eye causes only the opposite pupil to constrict, this indicates that the consensual reflex is intact, and any damage is likely to be associated with the oculomotor connections on the side where the direct reflex is lost. In summary, this reflex helps to determine if there is a problem with the optic or oculomotor nerves by eliciting pupillary constriction in both eyes when one eye is exposed to light.