The ciliary body is an important part of the eye that is concerned with optic accommodation as well as the production of aqueous humour (the fluid that occupies the space between the iris and the lens).
A special structure called the zonule is responsible for holding the lens in its place.
The ciliary muscles are rounded, smooth muscles that hold the zonules in place and bring about their contraction or relaxation to alter the shape of the lens.
This adjustment allows the lens to accommodate light arriving from different directions and distances and leads to proper image formation on the retina.