At 91 years of age, Robert Irwin, one of the founding masters of California’s experientially-pitched Light and Space movement, is currently staging what may well be his final gallery show of new work at Pace (through Feb. 22). “Just look at me,” he said, by phone, from his San Diego living room. “Man, that New York show is obviously my swan song.”

And indeed, over the past half-decade Mr. Irwin has been so racked by physical ailments, especially near-harrowing chronic back pain, that he hardly ever leaves his house, except occasionally to venture to his studio with the aid of his assistants. It has been years since he has been able to visit any of his recent exhibitions, notably including his legendary transformation (15 years in the making) of a dilapidated onetime military hospital at the Chinati Foundation in Marfa, Texas.

The Pace show consists of yet another departure. Over those same 15 years, Irwin had been deploying ever more complex variations on long color-saturated fluorescent light shafts vertically mounted in varying configurations against white walls or translucent scrim expanses. To attain their often astonishing hues, he’s been meticulously wrapping the individual bulbs in layers of theatrical gels, sometimes more than 10 thick. When displaying the arrays, some of the bulbs would be turned on, some not — many some of the time, others never — with the look of those arrays changing radically with each iteration.