Lately I’ve been seeing this thing on my computer screen and scared to death it represented some kind of retina damage. But instead, it is the normal effect of polarized light.
Sometimes life is like Scooby-Doo. You get a little mystery and then it gets solved.
I’ve never seen it on my computer, but I stumbled across a device someone built, consisting of a rotating sheet of polaroid in front of a back-lit piece of diffusing glass. The rotating movement made the figure particularly visible.
Some people are more sensitive to it than others.
For more info, see Jearl D. Walker’s “Flying Circus of Physics” (For references), or M. Minnaert’s “The Nature of Light and Color in the Open Air”