The ciliary muscle is located in the eye and surrounds the lens. It contracts or relaxes in order for an individual to see at multiple distances. When it contracts, it pulls forward, moving to a frontal portion to relax the fibers that hold the lens in place; this process also allows it to take on a more spherical shape to provide short range focus, according to Reference.com.
The ciliary body includes smooth muscle fibers. According to HowStuffWorks, the lens is a biconvex lens. However, unlike the optical lenses created by man, the eyes are able to fine tune their lenses to improve focus. The ciliary body is also responsible for secreting aqueous humor, the clear fluid found in the front part of the human eye. The eye keeps the aqueous humor in balance by draining excess through the canal of Schlemm. Blockage of this exit leads to abnormal pressure in the eye through a disease known as glaucoma.
In addition to the ciliary muscles, the eye has dilator muscles that control the iris and pupil, which adjust the amount of light they allow into the eye. The iris of the eye works like the iris of a camera to optimize the opening size for the best possible vision, according to HowStuffWorks.