Op art is an art movement that includes paintings, sculptures and prints that rely on optical illusions or other techniques that alter perception for particular effects. The name "op art" is short for "optical art."
Emerging in the mid-1960s in America and later in Europe, op artists were influenced by concurrent psychological research in Gestalt theory and psychophysiology. Artists including Victor Vasarely, Bridget Riley, Yaacov Agam and François Morellet utilized techniques including reversible perspective, line interference and chromatic vibration to produce startling effects. The effects exhibited in these artworks, especially those by Agam, depended on the perspective of the viewer.