On the way to the Visual Cortex the ganglion-cell axons pass two second-level targets, the Lateral Geniculate Nucleus(LGN) and the Superior Culliculus(SC).
Caused by branching of the axons, processing in both LGN and SC are done in parallel with all information from the retina retained.
The fibers reaching the LGN comes from the cone-rich areas of the eye, representing high visual acuity. The SC instead, receives fibers from rod-rich areas in the peripheral zones of the eye, where visual acuity is less but detection of movement is greater. Neurons in the SC also receives auditory information and vestibular information about head position, as well as visual information that has already been processed and fed back from the neurons of the primary visual cortex. Because it receives all this input, the culliculus is thought to serve as a subcortical center for integrating the information that we use to orient ourselves spatially in a moving world. The SC is also able to drive the extraocular muscles to rotate the eye to the point where movement occured[1].