It controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humor into Schlemm's canal.

The effect of contraction is to decrease the diameter of the ring of ciliary muscle causing relaxation of the zonule fibers, the lens becomes more spherical, increasing its power to refract light for near vision.

[citation needed] The parasympathetic tone is dominant when a higher degree of accommodation of the lens is required, such as reading a book.

[15] Open-angle glaucoma (OAG) and closed-angle glaucoma (CAG) may be treated by muscarinic receptor agonists (e.g., pilocarpine), which cause rapid miosis and contraction of the ciliary muscles, opening the trabecular meshwork, facilitating drainage of the aqueous humour into the canal of Schlemm and ultimately decreasing intraocular pressure.

The suffix -ary originally occurred in loanwords from Middle English (-arie), Old French (-er, -eer, -ier, -aire, -er), and Latin (-ārius); it can generally mean "pertaining to, connected with", "contributing to", and "for the purpose of".