Bridget Riley gave abstract art the neurological impact of a mind-altering substance six decades ago when she started painting black-and-white spirals, waves and folds that confuse perception. A new exhibition to mark her 90th birthday earlier this year is called Pleasures of Sight, but the happiness she provokes in us is really in our brains. The delight of Riley’s art comes from the way she can make the mind see mountains and valleys, vertigo-inducing swoops and sudden movements that are not there. She is the only British painter to change the history of abstract art. In the 1950s, the most exciting art in the world came from New York. Jackson Pollock, whose work made a huge impression on Riley when she saw his famous show at London’s Whitechapel Gallery in 1958, made painting feel like a living “action” instead of a framed picture: he and the other American action painters created art on an embracing scale, one that you could fall into. Riley felt its power yet changed its nature. Since the start of the 60s she has painted on that same big, open, potentially limitless scale yet with a scientific realism. Instead of relying on woozy romantic feeling, she aims for quantifiable, physical results. Riley trained in a postwar Britain where “proper” art meant an accurate picture. She was a good student whose early portraits and life studies remain impressive. As a teenager she painted a copy of Jan van Eyck’s Portrait of a Man in a Red Turban in the National Gallery. She dived deep into the folds and shadows of the red headgear the man is wearing: like the 15th-century master, she was interested in the way paint can weave illusions of depth and solidity on a flat surface. Van Eyck was one of the first artists to paint convincing illusions of space. Perspective, the technique of doing this, is at the heart of Riley’s illusions. She, too, paints carefully calculated spatial fictions – but instead of convincing us we are looking at folded cloth or into a room, she makes us see bulbous projections and sublime chasms that break the veil between art and us, outer and inner experience. For all her science, she is a romantic at heart. Like her contemporaries who took LSD, she uses the brain’s chemistry to get at transcendental experiences. The mysticism in Riley’s modernism became increasingly apparent. In the later 1960s she moved away from the black-and-white “op art” she had become famous for, partly because she was disgusted to see her style copied in ads and department store windows. She began to paint equally rigorous but more subtle sweeps of alternating colour. 19th-century painter Georges Seurat is another of her influences: in 1960 she painted her own masterpiece of pixelated colour, a captivating Tuscan view called Pink Landscape. In her colour abstractions she creates magical, sizzling effects by setting greens, reds and purples side by side. How do Riley’s grand, intellectual developments over more than 60 years relate to the joys and vicissitudes of a life? Who knows. Without being reclusive, she has calmly rejected all the cliches of artistic fame, creating art that can seem utterly impersonal but always spiritually intense. The emotional highs and lows (mostly highs) are yours as you move through a room where her art hangs, feeling elated, liberated, and occasionally even seasick. She offers, not an introspective expressionist self-portrait, but a shared, universal music. An Ode to Joy. Bridget Riley: Pleasures of Sight is at The Lightbox, Woking, 18 December to 10 April New perspectives: four works by Bridget Riley Movement in Squares, 1961 If there was ever an artist whose work you need to experience in its full glory in a physical space, it’s Riley. Yet Tthe eye-boggling psychedelic power of Movement in Squares is so infectious it even works on small scale in print or on screen. Your mind splits open as you gaze on this chessboard pattern that collapses into a diving chasm. Op – short for optical – was the glib name given to Riley’s shocks to perception. She became a star but this thinking persont, unwillingly sucked into pop culture, she lamented that: “It will take at least 20 years before anyone looks at my paintings seriously again.” It has been 60 years and Movement in Squares remains a masterpiece of modern art. Ecclesia, 1985 It might seem that, since rejecting her early pop star fame, Riley has worked in isolation from her times. When she painted Ecclesia, she was a trustee of the National Gallery, and selected a show there of great colourists of the past, from Titian and Veronese, to Rubens and Poussin. Riley has recently reaffirmed her commitment to the old masters with a wall painting in the National Gallery’s lobby. Yet Ecclesia is nothing if not modern – and it seems rawly, brashly of its time, pulsing with the vulgar capitalist energy of 1980s Manhattan or London. You could play early electro-dance music against these vertical bars of merciless colour. Fête, 1989, top The artist who shook the swinging 60s is as sharp, new and relentless as ever as she enters another phase of pure abstraction. Riley’s life of looking at art and the world is in this cascading restless progress of coloured lozenges. Fête is a distillation of the nature of art itself: colour and movement flit through it as powerfully as they do in a huge oil painting of frolicking wine harvesters or a fresco of lovemaking gods. Riley’s deep knowledge of art, and deeper appetite for life, pulse within it.