Final answer:
The optic nerve (CN II) is responsible for vision, transmitting visual information from the retina to the brain.
Step-by-step explanation:
The function of the optic nerve (CN II) is related to vision. Specifically, the optic nerve carries visual information from the retina, located at the back of the eye, to the brain where this information is processed, allowing us to see. Several common vision problems can affect the function of the optic nerve, such as myopia (nearsightedness), hyperopia (farsightedness), and presbyopia (age-related decline in close vision). Given the options provided in the question, Option 3: Vision is the correct answer to what function the optic nerve serves.