Family Nurse Practitioner Exam

Which cranial nerve is responsible for the corneal reflex during an eye exam?

1. CN II

2. CN III

3. CN IV

4. CN V

The correct answer is: CN V

The cranial nerve responsible for the corneal reflex during an eye exam is indeed the fifth cranial nerve, known as the trigeminal nerve (CN V). This nerve plays a critical role in sensory functions, particularly in the face, which includes providing sensation to the cornea. When the cornea is stimulated, such as by a foreign object or during an exam, sensory information is transmitted through the trigeminal nerve to the brain. This stimulus then prompts a reflexive action through the facial nerve (CN VII), which results in blinking. This reflex is important as it protects the eye from potential damage and maintains ocular health. The corneal reflex is one of the key assessments in neurological examinations as it helps evaluate both sensory and motor pathways. In contrast, while CN II (optic nerve) is responsible for vision and the sense of light, CN III (oculomotor nerve) primarily controls most eye movements and pupil constriction. CN IV (trochlear nerve) is mainly involved in the movement of the superior oblique muscle for turning the eye downward and laterally. Each of these nerves has distinct functions that do not include mediating the corneal reflex. Thus, the trigeminal nerve's role in this reflex underscores