The two main functions of the lens of the eye are to focus light onto the retina and to help the eye focus on objects at various distances. The lens of the eye is a rubbery, jellylike structure. It is located behind the cornea and is held in place by tendons that are attached to a set of muscles called ciliary muscles.
The tendons and ciliary muscles help the eye to focus by either relaxing or pulling the lens, allowing it to become either more spherical or flatter in shape. This adjustment in the shape of the lens permits the eye to focus on objects at various distances. The adjustment occurs very quickly, allowing the eye to focus on a nearby object at one moment and a far-away object at the next moment.
Sometimes the lens of the eye does not function properly or needs extra assistance to focus on objects correctly. Eyeglasses or contact lenses provide this assistance. The lens of the eye may also become cloudy with age, which is a condition known as a cataract. Lens replacement surgery is available for people with cataracts. The lens of the eye may also deteriorate with age, and its ability to adjust from a distant to a near focus declines. Many older individuals require reading glasses to correct this issue.