The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle and ciliary processes.^[1] It is part of the uveal tract—the layer of tissue which provides most of the nutrients in the eye. There are three sets of ciliary muscles in the eye, the longitudinal, radial, and circular muscles. They are near the front of the eye, above and below the lens. They are attached to the lens by connective tissue called the zonule of Zinn, and are responsible for shaping the lens to focus light on the retina.

When the ciliary muscle relaxes, it flattens the lens, generally improving the focus for farther objects. When it contracts, the lens becomes more convex, generally improving the focus for closer objects.