What effect does the ciliary body have on the lens?

The ciliary body plays a crucial role in adjusting the shape of the lens to facilitate focusing on objects at various distances, a process known as accommodation. When the ciliary muscles within the ciliary body contract, they relax the tension on the zonules (or zonular fibers) that connect the ciliary body to the lens. This allows the lens to become more rounded and thick, which is necessary for focusing on nearby objects. Conversely, when the ciliary muscle relaxes, the tension on the zonules increases, causing the lens to flatten for focusing on distant objects.

This dynamic ability of the ciliary body to control the lens shape enables clear vision across different distances, making it an essential component of the eye's optical system. Other options, while related to vision, do not accurately describe the functions performed by the ciliary body. For instance, the ciliary body does not directly prevent lens cloudiness or change the color of the lens, nor is its primary role maintaining the lens's position, although it does support the lens via zonular fibers.