CRT screens can flicker at a rate of speed that humans can't consciously notice -- but it's there nonetheless.  The flickering has no effect whatsoever on some people, while it can cause headaches in others.  IIRC, I've even heard of it making some people sick.  The effect is so bad for certain individuals that they can't (or at least they couldn't, prior to LCD's) use a computer.

I've heard of a very tiny percentage of people being similarly affected by fluorescent light bulbs / tubes.........which would be a serious handicap into today's world.

The flashing red eyes on a cartoon dragon sent a large number of television-watching Japanese children into a catatonic state: while at the same time having no effect on other children -- demonstrating that such sensitivities are a thing which varies widely from one person to another.

I posted an OT topic several months ago about a 'nonlethal weapon' that's currently under development for use by the military and police -- a flashlight that makes people sick.

http://www.foxnews.com/story/0,2933,292271,00.html

But I wonder if it'll be the same as with other light-sensitivity issues: where some people won't be affected by it at all?

Something To Do At 3:00AM