## **Core Concept**
The question tests the understanding of the **corneal reflex pathway**, which involves the afferent (sensory) and efferent (motor) components. The afferent pathway is mediated by the **trigeminal nerve (cranial nerve V)**, while the efferent pathway is mediated by the **facial nerve (cranial nerve VII)**. The corneal reflex involves both eyes blinking when one eye's cornea is touched.

## **Why the Correct Answer is Right**
The described response, where touching one eye's cornea results in only that eye blinking (absence of the consensual blink reflex), indicates a problem with the **trigeminal nerve (afferent pathway)** on the same side. This is because the afferent signal from the cornea is not properly transmitted to the brainstem, which then fails to send the efferent signal via the facial nerve to both eyes to blink. The **brainstem** integrates this reflex. A lesion affecting the **trigeminal nerve** would result in the loss of the afferent input, preventing the reflex arc from being completed, hence only the ipsilateral eye blinks.

## **Why Each Wrong Option is Incorrect**
- **Option A:** A lesion here would affect the motor part of the reflex (efferent pathway), leading to weakness or paralysis of the muscles of facial expression on the side of the lesion, not specifically abolishing the corneal reflex on one side.
- **Option B:** This would imply a problem with the motor part of the reflex (facial nerve), affecting the ability to blink on the side of the lesion, not specifically the afferent part of the reflex.
- **Option D:** This option does not directly relate to the specific reflex described and seems to imply a more central lesion which might affect both sides.

## **Clinical Pearl / High-Yield Fact**
A key clinical point is that the **corneal reflex** is crucial for protecting the eye. Its absence can lead to corneal ulcers and vision loss. When testing the corneal reflex, it's essential to compare the response in both eyes to assess for unilateral or bilateral lesions affecting the trigeminal or facial nerves.

## **Correct Answer: C.**