Here's how it works:

* Ciliary Muscles: These muscles are located within the eye, surrounding the lens.

* Lens: This transparent, biconvex structure focuses light onto the retina at the back of the eye.

* Focusing: When the ciliary muscles contract, they relax the suspensory ligaments that hold the lens in place. This allows the lens to become more rounded, increasing its refractive power and focusing light on the retina for near vision. When the ciliary muscles relax, the lens becomes flatter, decreasing its refractive power for distant vision.

This process of adjusting the lens shape is called accommodation.