List of Figures

1 Horizontal section of the eye, showing terms  mentioned in the text 7

2 The pathway of information from retina to brain 14

3 The Ponzo Illusion 17

4 An impossible object 17

5 The Necker Cube 18

6 The principle of refraction 21

7 Refraction by a lens 22

8 Refraction of light from near and far objects 22

9 The principle of astigmatism 24

10 Fusion figures 57

11 The domino board 66

12 Measuring visual acuity 99