ABSTRACT
The eye is often compared to a camera. It does, of course share many of the optical principles of a modern camera but it is a far more sophisticated instrument than any manufacturer has dreamed up yet. It can do two things that no camera, however refined, can do; it can repair itself, to an extent at least, when it is damaged and it can alter the focal length of one of its refracting mechanisms, the lens, by changing its shape. On the other hand, it is subject to the same ageing process as all living tissue. In trying to understand some of the difficulties of elderly people with poor sight, it is useful to examine how each of the main components of the optical system changes with advancing years.
