A type of abstract art that exploits certain optical phenomena to cause a work to seem to vibrate, pulsate, or flicker. It flourished mainly in the 1960s; the term was first used in print in the American magazine Time in October 1964 and had become a household phrase by the following year, partly through the attention given to the exhibition ‘The Responsive Eye’ held at the Museum of Modern Art, New York, in 1965. This was the first international exhibition with a predominance of Op paintings. The development of Op art as a recognizable movement had begun a few years earlier than this, in about 1960, the works and theories of Josef Albers being among the main sources. The devices employed by Op artists (after-images, effects of dazzle and vibration, and so on) are often elaborations on the well-known visual illusions to be found in standard textbooks of perceptual psychology, and maximum precision is sought in the control of surfaces and edges in order to evoke an exactly prescribed retinal response. Many Op paintings employ repeated small-scale patterns arranged so as to suggest underlying secondary shapes or warping or swelling surfaces. This kind of work can retain much of its effect in reproduction, but Op art also embraces constructions that depend for their effect on light and/or movement, so Op and Kinetic art sometimes overlap. The two most famous exponents of Op art are Bridget Riley and Victor Vasarely. Their work illustrates the considerable impact that Op made on fashion and design in the 1960s—its instant popular success (accompanied by a fairly cool critical reception) is hard to parallel in modern art. Op art became something of a craze in women's fashion and in 1965 Riley unsuccessfully tried to sue an American clothing company that used one of her paintings as a fabric design. One of Vasarely's designs was used on the plastic carrier bags of France's chain of COOP stores. Among other exponents of Op art the best known is probably the American Richard Anuszkiewicz (b1930), a former pupil of Albers; his work is typically concerned with radiating expanses of lines and colours.