Lens of the eye

Animation of the lens of the eye, showing the shape changes that help to focus incoming light, a process called accommodation. The lens (grey) is flexible, and is attached by fibres (white) to the muscles of the ciliary body (red, above and below lens). When the muscles are relaxed the lens has a shorter, rounder shape, with more focussing power. When the muscles contract, the fibres pull the lens into a thinner shape, which has a longer focal length. The change of shape of the lens allows fine-tuning of focus. The majority of the focussing power of the eye is in the cornea (black) at the front of the eye.