Which cranial nerve is primarily responsible for eye abduction?

The cranial nerve responsible for eye abduction is the abducens nerve, which is cranial nerve VI. This nerve specifically innervates the lateral rectus muscle, allowing for the outward movement of the eye away from the midline. When the lateral rectus muscle contracts, it pulls the eye laterally, enabling the abduction movement necessary for looking to the side.

The other cranial nerves listed have different functions: cranial nerve IV (trochlear nerve) innervates the superior oblique muscle, contributing to downward and lateral eye movement; cranial nerve III (oculomotor nerve) is responsible for most eye movements, including adduction, elevation, and depression, but not abduction; and cranial nerve II (optic nerve) is primarily involved in vision, transmitting visual information from the retina to the brain. Thus, cranial nerve VI is uniquely suited to facilitate the abduction of the eye.