The eye is the main organ for sensing light, and its design is optimized for capturing light and forming images. The eye is, in many respects, like a camera. The optical system of the eye forms an image on the retina, whereas the camera lens forms its image on film. The camera must be focused by changing the distance from the lens to the film. However, a change in the configuration of the crystalline lens (human lens) occurs when the eye needs to focus at different distances (accommodation). This involves alterations in curvature, thickness, and refractive index of the lens. A change in the axial length of the eye is not involved.