First and foremost, Op Art exists to fool the eye. Op compositions create a sort of visual tension, in the viewer's mind, that gives works the illusion of movement. For example, concentrate on Bridget Riley's Dominance Portfolio, Blue (1977) - for even a few seconds - and it begins to dance and wave in front of one's eyes. Realistically, you know any Op Art piece is flat, static and two-dimensional. Your eye, however, begins sending your brain the message that what it's seeing has begun to oscillate, flicker, throb and any other verb one can employ to mean: "Yikes! This painting is moving!"
Because of its geometrically-based nature, Op Art is, almost without exception,non-representational.
The elements employed (color, line and shape) are carefully chosen to achieve maximum effect.
The critical techniques used in Op Art are perspective and careful juxtaposition of color (whether chromatic [identifiable hues] or achromatic [black, white or gray]).
In Op Art, as in perhaps no other artistic school, positive and negative spaces in a composition are of equal importance. Op Art could not be created without both.