This is another good example of Op Art. Bridget Riley frequently used black-and-white images such as this to produce the effect of an optical illusion in her artworks. Here we see a unique mix of reversing patterns that narrow and shrink in circular fashion toward a round, empty center, which our eye naturally looks to. When you're looking at the center of the work, however, do you notice the way the black lines all around it seem to be moving? This is an optical trick easily achieved once learned but requiring exact precision in order to work. Riley's canvases had to be mathematically structured in order to produce the proper effect. In order for you to get the full effect, you might want to enlarge the image by clicking on it; but I wouldn't blame you for not looking at it too long. This kind of art gives me headaches.