Postsynaptic parasympathetic fibers leave the ciliary ganglion in multiple (six to ten) short ciliary nerves. These nerves enter the posterior aspect of the eyeball to innervate the sphincter pupillae and ciliaris muscles. The sphincter pupillae constricts the iris. The ciliaris muscle changes the shape of the lens, allowing the eye to focus on nearby objects (accommodation). Neither of these muscles is under voluntary control.
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