How does the oculomotor nerve (CN III) contribute to vision?

The oculomotor nerve, also known as cranial nerve III, plays a crucial role in vision by facilitating both pupil constriction and eye movement. It is responsible for the motor control of most of the extraocular muscles, which are essential for moving the eyeball in different directions. This includes movements such as looking up, down, and inward.

In addition to motor functions, the oculomotor nerve also has a significant autonomic component that controls the constriction of the pupil through the parasympathetic pathways. This process, known as pupillary light reflex, helps regulate the amount of light entering the eye, optimizing vision under varying lighting conditions.

The other options pertain to functions controlled by different cranial nerves, with no direct link to the oculomotor nerve. Hearing and balance are primarily mediated by the vestibulocochlear nerve (CN VIII), while facial sensations are the responsibility of the trigeminal nerve (CN V). Taste sensations are managed by the facial nerve (CN VII) and the glossopharyngeal nerve (CN IX), not the oculomotor nerve. Thus, option A correctly identifies the dual role of the oculomotor nerve in vision.