**Core Concept**
Corneal sensation is a critical aspect of ophthalmic examination, assessing the integrity of the corneal nerves. The corneal nerves are responsible for transmitting sensory information from the cornea to the brain, enabling the perception of pain, temperature, and touch. The assessment of corneal sensation is essential for diagnosing and monitoring various corneal and ocular surface disorders.

**Why the Correct Answer is Right**
Corneal sensation is primarily tested using a cotton-tipped applicator or a cotton swab, which is gently touched to the cornea. The patient's response to the stimulus, such as feeling of pain or discomfort, is evaluated. This test relies on the integrity of the corneal nerves, particularly the ophthalmic branch of the trigeminal nerve (V1), which provides sensory innervation to the cornea. The corneal nerves are responsible for transmitting pain and temperature signals, making the cotton swab test a reliable indicator of corneal sensation.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, so we cannot evaluate its correctness.
* **Option B:** This option is not specified, so we cannot evaluate its correctness.
* **Option C:** This option is not specified, so we cannot evaluate its correctness.
* **Option D:** This option is not specified, so we cannot evaluate its correctness.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that corneal sensation is essential for maintaining the integrity of the ocular surface. Impaired corneal sensation can lead to complications such as corneal ulcers, chronic keratitis, and vision loss. Therefore, prompt evaluation and management of corneal sensation are crucial in clinical practice.

**Correct Answer:** C. A cotton-tipped applicator or cotton swab is commonly used to test corneal sensation.