To be read with a trembling eye. Like many people, Mister Bijou was unnerved as a child by the thought that maybe the colours he saw were not exactly the same as seen by other people. We might have some general agreement as to what constitute red or blue of green, but . . .
Even so, Mister Bijou is not sure he ever talked out loud about it. But he does know a decade or so ago he truly startled a group of people when he recounted something which had been niggling him for years. To wit, how it takes one tenth of a millisecond for light to penetrate the retina, hit those cones and rods, and finally get processed in the synapses and neurons of the brain to produce "what we see".
That's to say, that itty-bitty tenth of a milisecond gap means what we "see" has already happened. Which means (doesn't it?) that we visually live our lives in the constant past. Thus reality -- the here and now -- is an illusion. Maybe Mister Bijou is missing something?
Anyway, Mister Bijou remembers those who were "present" at the telling of this, as if touched by fire, backed away a yard or two. So it goes.
Perhaps this will clarify, The Eye: A Natural History by Simon Ings -- timesonline