The ciliary muscles in our eyes are how we adjust to something that is far or something that is close based on the index of refraction. For example, if we need to see something close, the ciliary muscles will contract, causing the suspensory ligaments to loosen and the lens to become rounder - how we accommodate for near vision. To accommodate for far vision, ciliary muscles relax and vice versa for the suspensory ligaments = lens becomes flatter.
