The cornea located at the front of the eye refracts light onto the lens. The lens, on the other hand, refracts light precisely on the surface of the retina. The shape of the lens can be changed by contracting the ciliary muscles, which makes us able to focus our gaze near or far.

• When focusing on a distant object the ciliary muscles are at rest.
• When focusing on a nearby object the ciliary muscles contract. 

The image illustrates the contraction of the ciliary muscle when looking at a distant or a nearby object. The parts of the eye: 1. ciliary muscle, 2. pupil, 3. lens.

When we focus on an object in a distance (upper image), the ciliary muscles are at rest, suspensory ligaments are stretched, and the lens is thin. Light is refracted only slightly.

When we look at something up close (lower image), the ciliary muscles are contracted, the suspensory ligaments loosen, and the lens becomes thicker, more convex. Light is refracted strongly. With age, the convexity of the lens decreases.

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