What is the primary role of the optic nerve?

The primary role of the optic nerve is to transmit visual information from the retina to the brain. Once light enters the eye and is focused on the retina, photoreceptor cells in the retina convert the light into electrical signals. These signals are then relayed through the optic nerve, which carries this visual information to the visual cortex in the brain for interpretation. This process is crucial for our ability to perceive the world around us visually. The optic nerve, therefore, serves as the critical communication link between the eye and the brain, allowing us to see and interpret visual stimuli.

The other roles listed, such as focusing light, controlling eye movement, and regulating pupil size, are important functions associated with different parts of the eye and ocular system, but they do not pertain to the primary function of the optic nerve itself. Focusing light is primarily achieved by the lens and cornea, eye movement is controlled by extraocular muscles, and pupil size is regulated by the iris.