ABSTRACT
Our brains are marvellous 1.3 kilo lumps of fats and proteins living in dark bone boxes. They control nearly all of our bodily processes: breaths, heartbeats, some gut functions and many other chores of which we are, gratefully, unconscious. Almost as a sideline, they receive and keep all the information we get about our worlds, ourselves and the shifting and muddled representations and projections of present, past and future that we call our 'consciousness'. Visual illusions show that there are many different levels at which the changes that age brings to our nervous systems affect our interpretations of the world. At each of these stages, physical changes affect the amount and kinds of light that travel through the eye and thus the quality of the image on the retina. The cornea, like a carelessly handled spectacle lens, gradually becomes scratched and damaged. It also takes on a yellow clouding. Corneal damage scatters light and blurs the eventual image on retina.
