Viewer Participation
Unlike Conceptual Art, Optical Art, or Op Art, is really concerned about engaging the viewer. Various straight, concentric and undulating lines are used to create various types of illusions, the most important of which is movement. Color is also often used to manipulate these illusions.
I don't think Op Art creators are as pretentious as Conceptual Artists. Firstly, there is quite a high degree of skill and knowledge required to make Op Art. Secondly, the goal is really to amuse, or at least to engage, the viewer. Unlike Conceptual Artists, who really work in their own vacuum and dogged seriousness, an Op Art piece only works if the viewer responds accordingly, and usually with surprise and pleasure.
The charm of Op Art is that it also is used often in fabrics.
Success has a real concrete definition.