op art (ŏp), movement that became prominent in the United States and Europe in the mid-1960s. Deriving from abstract expressionism, op art includes paintings concerned with surface kinetics. Colors were used in creating visual effects, such as afterimages and trompe-l'oeil. Vibrating colors, concentric circles, and pulsating moiré patterns were characteristic of op works by such artists as Victor Vasarely, Richard Anusziewicz, Bridget Riley, Yaacov Agam, and Larry Poons. A comprehensive exhibition of op art, entitled "The Responsive Eye," was organized by the Museum of Modern Art, New York City, in 1965.