Abstract
The process of human vision has been described as 'the most extraordinary and the most complicated functioning system on earth' (Gregory, 1970). We are so used to being able to see that it is hard for us to realize what a marvellous process it is. We are able, effortlessly, without making any conscious adjustments, to focus on far-away stars, on tiny print, on moving objects against a background of stationary ones and to know which is which and to do this in very dim light or in very bright light. What man-made machine could accomplish anything remotely like the eye and brain are able to achieve?