The curvature of the eye lens can be modified to some extent by the ciliary muscles and consequently its focal length can be changed. The ability of the eye lens to adjust its focal length is called accommodation. In order to focus far-off objects, the ciliary muscles relax, they pull the crystalline lens outward making it thin and thus increasing its focal length. Similarly, to focus nearby objects, the ciliary muscles contract to thicken the eye lens in order to decrease its focal length. Thus, the images of the objects are clearly focussed on retina.