second cranial nerve; conveys visual information from the retina to the brain; carries the axons of the retinal ganglion cells which sort at the optic chiasm and continue via the optic tracts to the brain; the largest projection is to the lateral geniculate nuclei; other important targets include the superior colliculi and the suprachiasmatic nuclei; though known as the second cranial nerve, it is considered part of the central nervous system.