“[O]ptical art teaches its beholders a lesson taught by psychedelic
drugs at a considerably higher level of risk: it insists on the
absolute otherness of a world beyond us by dramatizing the threshhold
at which our ability to interpret that world begins to degrade and
disintegrate.”

—Dave Hickey, introduction to Optic Nerve: Perceptual Art of the 1960s, by John Houston, 2007.