What is the primary function of the ciliary body in the eye?

The primary function of the ciliary body in the eye is to manage the shape and position of the lens. This structure is crucial for the process of accommodation, allowing the lens to change shape in response to visual demands. When the ciliary muscle contracts, it reduces tension on the zonule fibers that hold the lens in place, enabling the lens to become more rounded for near vision. Conversely, when the ciliary muscle relaxes, the tension increases, flattening the lens for distance vision. This ability to adjust the lens shape is essential for focusing light on the retina, thereby improving visual clarity at various distances.

Although regulating light entry into the eye is an important function of the iris, the ciliary body's role is more directly related to lens management. Eye movement is primarily controlled by extraocular muscles, while tear production is facilitated by the lacrimal glands. Understanding these distinctions clarifies the unique and vital role that the ciliary body plays in vision.