Iris (anatomy) surface projects as the dilator muscles. The high pigment content blocks light from passing through the iris to the retina, restricting it to the pupil. The outer edge of the iris, known as the root, is attached to the sclera and the anterior ciliary body. The iris and ciliary body together are known as the anterior uvea. Just in front of the root of the iris is the region referred to as the trabecular meshwork, through which the aqueous humour constantly drains out of the eye, with the result that diseases of the iris often have important effects on intraocular
Ciliary muscle parasympathetic postganglionic fibers are part of cranial nerve V (Nasociliary nerve of the trigeminal), while presynaptic parasympathetic fibers to the ciliary ganglia are from the oculomotor nerve. The postganglionic sympathetic innervation arises from the superior cervical ganglia. Presynaptic parasympathetic signals that originate in the Edinger-Westphal nucleus are carried by cranial nerve III (the oculomotor nerve) and travel through the ciliary ganglion via the postganglionic parasympathetics fibers which travel in the short ciliary nerves and supply the ciliary body and iris. Parasympathetic activation of the M3 muscarinic receptors causes ciliary muscle contraction, the effect of contraction is to decrease the diameter