Once more light enters the eye, we can somewhat see even in darkness. In pitch darkness, where there is no light reflected from anywhere, we would be unable to see anything. Figure below shows how an eye focuses objects at a far off distance from where parallel rays of light are impinging on the eye. When the eye is focusing distant objects, the ciliary muscles are relaxed and the lens of the eye is less convex. The ciliary muscles adjust in such a manner that the size of the eye is the focal length of the convex lens.
Figure below shows how an eye focuses objects at a near by distance.
In this case the ciliary muscles contract, making the central portion of the convex lens bulge. The focal length of the convex lens now decreases. The rays from the object, after passing through the lens converge at the focal plane, which is the retina. Thus our eyes can see distant as well as nearby objects by changing the shape of the lens. This ability to focus objects at various distances is called as the accommodation of the eye.