This causes the thickness in the middle part Vision 20/20 Protocol Review of the lens to be less than it could be. If the ciliary muscle were to contract, it would form a somewhat smaller ring. When this happens, the outward pull on the lens is less than before. As a result, the middle part of the lens becomes thicker. The more the ciliary muscle contracts, the thicker the middle of the lens becomes.
The ability of the eye to vary the thickness of the crystalline lens is essential in order for the eye to see clearly both near objects and far objects. In order to form a clear image on the retina, the light rays coming from a near object must be bent more than the light rays coming from a far object.
The thicker the middle of the lens, the more the lens bends the light rays. Therefore, whenever the eye focuses on a near object, the ciliary muscle contracts and forms a smaller ring in order to allow the middle of the lens to become thicker. But when the eye focuses on a far object, the ciliary muscle relaxes and forms a larger ring, thus causing the suspensory ligament fibers to pull the edges of the lens outward. As a result, the middle of the lens is less thick.