User error, IMO.
I'm of the opinion that if your monitor showing a pure white screen is painful, then either your brightness is too high or you don't have adequate ambient light.
It’s still not the same as a black screen that’s not emitting light.
You said it yourself actually: lcd monitors do require ambient light to not be painful. CRTs could do without.
When I was a kid, if I was playing NES/SNES games on my TV with no lights on, after an hour or so, my eyes were burning.
Anyway I've never been burned burned by tv or monitor lighting, but I've started to see less well in the dark just a few years after switching to lcds. Being under 30, maybe closer to 25 than 30. To the point that my wife asks me why I keep turning lights on at dusk in rooms where she sees perfectly with what's left of the sunlight.
Some PWM flicker might reach a frequency that is low enough to bother you, I've read about people who bought a brand new LCD TV and had to return it due to headaches, supposedly attributed to the rate of flicking by the PWM.
Some monitors are sometimes even reviewed as not employing a PWM thus being easier on the eyes.
And I definitely notice the flicker in a CRT, especially when I'm not looking straight at it (oddly). Heck, I see the flicker of LED Christmas lights.
The problem them is that your brain might be subconsciously sensitive to some specific flicker patterns, resulting in the aforementioned headaches.
