Touching the cornea assesses which cranial nerve?

Touching the cornea assesses which cranial nerve?

• A. Cranial Nerve II (CN II)
• B. Cranial Nerve IV (CN IV)
• C. Cranial Nerve V (CN V)
• D. Cranial Nerve X (CN X)

Answer: (C)

Touching the cornea primarily tests sensory input carried by the ophthalmic division of the trigeminal nerve. When the cornea is touched, signals travel through the nasociliary branch of V1 to the trigeminal sensory nucleus, triggering the corneal reflex. The blink you see is produced by the facial nerve acting on the orbicularis oculi as the efferent limb. So, corneal sensation is a function of the trigeminal nerve. The other nerves listed aren’t responsible for corneal sensation—optic nerve for vision, trochlear for a specific eye muscle, and vagus for various autonomic/motor functions not related to corneal sensation or the corneal reflex.

Touching the cornea primarily tests sensory input carried by the ophthalmic division of the trigeminal nerve. When the cornea is touched, signals travel through the nasociliary branch of V1 to the trigeminal sensory nucleus, triggering the corneal reflex. The blink you see is produced by the facial nerve acting on the orbicularis oculi as the efferent limb. So, corneal sensation is a function of the trigeminal nerve. The other nerves listed aren’t responsible for corneal sensation—optic nerve for vision, trochlear for a specific eye muscle, and vagus for various autonomic/motor functions not related to corneal sensation or the corneal reflex.