Each optic nerve is composed of approximately one million axons from retinal ganglion cells. These axons exit the eye through the lamina cribrosa-where they are most susceptible to damage from either elevated intraocular or intracranial pressure-intermingle with axons from the opposite eye to form the optic chiasm and optic tracts, and finally synapse at the lateral geniculate bodies. Optic atrophy results from damage to the ganglion cell (ascending) or to the axon anywhere along its course from the eye to the lateral geniculate body (descending).