Which action should a nurse take to assess cranial nerve III during a neurological examination?

Assessing cranial nerve III, also known as the oculomotor nerve, primarily involves evaluating its function, which includes controlling pupillary reaction to light and the movement of the eye. Checking the pupillary response to light is a fundamental part of neurological examinations because it not only assesses the function of cranial nerve III but also incorporates the involvement of cranial nerve II (the optic nerve) for the sensory input.

When light is directed into one eye, both pupils should constrict due to the consensual reflex, which is mediated by these nerves. This test is critical for determining whether the pathways for visual input and motor output are intact, which can reveal potential neurological issues such as increased intracranial pressure or other impairments.

The other actions listed, while important in different contexts, assess different cranial nerves or functions. Testing the sense of smell is related to cranial nerve I, assessing facial symmetry typically evaluates cranial nerve VII, and evaluating the range of eye movement assesses cranial nerves III, IV, and VI. However, the direct test for cranial nerve III's integrity is best represented by checking the pupillary response to light.