The afferent limb of the circuit This limb contains the main structures; the retina that contains the retinal ganglion axons in the optic nerve, chiasm and tract, the lateral geniculate body, and the visual cortex.[1] The efferent limb of the circuit This limb includes Edinger-Westphal nucleus and the oculomotor neurons. The main function of the Edinger-Westphal nucleus is to send axons in the oculomotor nerve to control the ciliary ganglion which in turn, sends its axons in the short ciliary nerve to control the iris and the ciliary muscle of the eye.