Mario's birth and defects (p. 312)
It was pain. Broken water had made several steps below them gleam. She seemed to James Incandenza to sort of turn in toward herself, hold herself low, curl and sink to a stairstep she barely made the edge of, hunched, her forehead against her shapely knees. Incandenza saw the whole slow thing in a light like he was Vermeer: she sank steadily from his side and he bent to hers and she then tried to rise. […] A bit ragged from an afternoon of Wild Turkey and low-temperature holography, James had thought Avril was dying right before his eyes.
Context
Mario's premature birth on the Back Bay brownstone staircase, in the seventh month of a pregnancy Avril never showed. Even the family's founding emergency reaches JOI as a lighting setup — Vermeer light, an afternoon of holography still on him — while he thinks his wife is dying the way his father died, on stairs. The scene where a son becomes an optical instrument opens with the father unable to see except optically.