Which cranial nerve is primarily associated with vision?

The optic nerve, also known as cranial nerve II, is primarily responsible for vision. It carries visual information from the retina in the eye to the brain, where it is processed to create the images we perceive. This nerve is essential for the function of sight, as it transmits the electrical impulses generated by light striking the photoreceptors in the retina directly to the visual cortex of the brain.

In contrast, the oculomotor nerve is primarily responsible for controlling most of the eye's movements, including the regulation of pupil size and maintaining an open eyelid, but it does not transmit visual information itself. The trigeminal nerve is involved in sensation from the face and has a role in motor functions such as chewing, rather than in vision. The facial nerve primarily controls the muscles of facial expression and is also involved in functions like taste and salivary gland stimulation, not vision.

Therefore, the association of the optic nerve with vision makes it the correct choice for this question.