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The oculomotor nerve is primarily responsible for controlling most of the eye's movements. This cranial nerve innervates several extraocular muscles, including the superior rectus, inferior rectus, medial rectus, and inferior oblique, which together allow for a wide range of eye movements, such as elevation, depression, adduction, and some degree of rotation.

In addition to motor functions, the oculomotor nerve also carries parasympathetic fibers that are important for pupil constriction and controlling lens shape for accommodation, further highlighting its significant role in ocular function.

While other cranial nerves contribute to eye movements, their roles are more specific. The abducens nerve, for example, primarily controls lateral eye movement by innervating the lateral rectus muscle, and the trochlear nerve is responsible for controlling the superior oblique muscle, facilitating downward and inward movements. The optic nerve, on the other hand, is solely responsible for vision and has no motor function in eye movements.

Thus, the oculomotor nerve's extensive control over a majority of the eye's movement capabilities makes it the key nerve in this context.