Which nerves are involved in the corneal reflex?

• A. Optic nerve (CN II) for sensation; Oculomotor (CN III) for blink
• B. Trigeminal nerve (CN V) for sensation; Facial nerve (CN VII) for blink
• C. Vagus nerve (CN X) for sensation; Accessory nerve (CN XI) for blink
• D. Trigeminal nerve (CN V) for blink; Facial nerve (CN VII) for sensation

Answer: (B)

The corneal reflex uses the trigeminal nerve for sensation and the facial nerve for blinking. When the cornea is touched, sensory receptors send signals through the ophthalmic division of the trigeminal nerve (CN V1) to the brainstem. There, the signal triggers the facial motor nucleus, which sends a motor command via the facial nerve (CN VII) to the orbicularis oculi muscle, causing the eyelids to close. This is why CN V provides the sensation part and CN VII provides the blink. The optic nerve doesn’t carry corneal sensation (it handles vision), the oculomotor nerve doesn’t control the blink, and the vagus or accessory nerves aren’t part of this reflex.