The ciliary body is the part of the eye anatomy that both contains the ciliary muscle and controls the shape of the lens. The ciliary body is also responsible for the secretion of the fluid at the front of the eye known as aqueous humor.
The ciliary body is a ring of tissue around the lens. The contraction of ciliary muscle fibers cause the lens of the eye to become rounded and focus on nearby objects. When those muscle fibers relax, the lens becomes elongated to allow for distance vision. As a person gets older, the ciliary body and its muscles lose their resilience, and reading and performing other close-up tasks become more difficult. This vision condition is known as presbyopia.