The advanced practice registered nurse (APRN) is assessing the cranial nerves during a physical examination. Which tool will the APRN use to test cranial nerve II (CN2)?

A. Alcohol prep is incorrect because it is primarily used for disinfection of the skin before procedures or injections. While essential for infection control, it does not provide any information about cranial nerve function, including visual acuity or optic nerve integrity. B. Cotton swab is incorrect because it is used to assess sensory function, such as testing light touch or pain sensation of the face for cranial nerve V (trigeminal nerve). Cotton swabs can also be used for testing corneal reflexes, but they do not evaluate vision, so they are not appropriate for testing cranial nerve II. C. Snellen chart is correct because cranial nerve II (optic nerve) is responsible for vision, specifically visual acuity. The Snellen chart provides a standardized method for evaluating clarity and sharpness of vision at a distance. During the assessment, the APRN asks the patient to cover one eye at a time and read letters of decreasing size from a set distance (usually 20 feet or 6 meters). This assessment helps identify reduced visual acuity, refractive errors, or optic nerve pathology. Testing each eye individually allows detection of unilateral vision deficits, which can indicate localized optic nerve damage, retinal disease, or neurological conditions affecting vision. D. Tuning fork is incorrect because it is used to assess hearing (cranial nerve VIII) or vibratory sensation in peripheral nerves, not visual function. While important in other neurological assessments, a tuning fork does not evaluate optic nerve function or visual acuity.