A lens is attached to the ciliary body by the suspensory ligament behind the pupil. It is transparent, elastic and bi-convex. Its diameter is 10 mm and thickness is 3.7-4.5 mm. There is no blood supply to the lens. Contraction-dilation of the ciliary muscle causes the lens to contract-dilate. With the help of the lens, the light rays coming from the object are reflected to certain parts of the retina.