The lens lies just behind the pupil and is protected in front by the aqueous fluid which exists between it and the cornea. The lens is held in place by a ligament attached to the ciliary muscle located at the front part of the |eye|. The lens refracts light to focus a sharp image on the retina. In a healthy person, the muscles of the elastic lens can change its shape to bring objects at different distances into focus. When looking at a distant object, the ciliary muscle relaxes and the lens has only a slightly curved shape. To focus on a near object, the ciliary muscle must contract, causing the lens to become more bulging and curved. However, if the eyeball is shaped so that the retina is too near (hypermetropia) or far (~myopia~) from the lens, objects will appear out of focus. This can often be corrected with prescription eyewear (|eye glasses| or contact lens). ~Astigmatism~ is caused by an irregular shape of either the cornea or the lens. It can also be corrected with |eye glasses|. A newborn baby is naturally farsighted and cannot focus on nearby objects for several months. Young children usually have normal eyesight, but this may change as they grow. Some older people have trouble focusing on both near and far objects because their lenses have lost their natural elasticity. This problem can be corrected with bifocal lenses.
