Answer
In the accomodation process, the ciliary muscles contract; this results in a relaxation of the zonular fibers. As a consequence, the lens becomes more convex and its focusing capacity increases.
Work Step by Step
The cornea plays a more important role than the lens in the process of focusing light rays on the retina. Nevertheless, all adjustments for distance vision are made by alterations in shape of the lens. These changes in lens shape are effected by the ciliary muscle under the control of parasympathetic fibers of the third (III) cranial nerve. When the ciliary muscles are relaxed the lens assumes a flattened ovoid shape as it is stretched by the zonular fibers; this facilitates focusing on distant objects. For optimal focusing on near objects, the ciliary muscle contracts ; this releases tension on the zonular fibers, and allows the elastic lens to assume a more spherical shape which increases its power of convergence.
