Final answer:
The nurse uses the technique of checking for pupillary constriction to light to test the function of the oculomotor nerve, which is part of the pupillary light reflex, assessing both optic and oculomotor nerves.
Step-by-step explanation:
To test the function of cranial nerve III, or the oculomotor nerve, a nurse would use the technique of pupillary constriction to light. This is part of the pupillary light reflex which involves sensory input through the optic nerve and a motor response through the oculomotor nerve to the ciliary ganglion, affecting the circular fibers of the iris, causing pupils to constrict under bright lighting conditions. This reflex assesses the afferent pathways via the optic nerve and the efferent pathways through the oculomotor nerve.
In addition to assessing eyelid movement, other techniques to test the oculomotor nerve include having the patient track a visual target like a pen tip through their visual field. This tests for proper conjugate eye movements. Coordination of these movements involves the extraocular muscles, which are innervated by the oculomotor, trochlear, and abducens nerves and connected by the medial longitudinal fasciculus.