Retina: The pupillary reflex pathway begins with the photosensitive retinal ganglion cells, which convey information via the optic nerve, the most peripheral, distal, portion of which is the optic disc. Some axons of the optic nerve connect to the pretectal nucleus of the upper midbrain instead of the cells of the lateral geniculate nucleus (which project to the primary visual cortex). These intrinsic photosensitive ganglion cells are also referred to as melanopsin-containing cells, and they influence circadian rhythms as well as the pupillary light reflex.