hpst Well, recently I think I've also shown myself that I can develop the same eyestrain I get on my CCFL if I read print for too long as well. I don't read print for long periods of time too often, so it was a good test to show that it kinda rules out the monitor causing the strain.
I have to stress that I have two separate and distinct eye comfort issues when it comes to computer screens. One, the issue I described above, which I attribute to just reading overuse and maybe forgetting about the 20/20/20 rule. Staring at a computer screen (or phone screen) most of my waking hours makes this a rather unsurprising issue to some degree (although most of modern society does it and they don't seem to have the same issues). The symptoms are aching eyeballs and a tension headache in the temples and and sometimes back of the head. I've had these headaches for over 12 years now.
The other issue, which causes very different types of pain/symptoms is whenever I look at an LED-backlit monitor. This issue started around 2011 when LEDs first hit the market. Instead of a dull vice-like pressure the issue in the paragraph above I described, this is a sharp headache pain deep inside my head, with prickling and pain towards the back of my eyeballs (around where the head of the optic nerve is). These symptoms come on in the span of a few minutes, and the pain can last hours/days with such a short "exposure" time. I do not get these symptoms if I do not look at these types of displays.
Only you and I think shiviawind have the type of symptoms/trigger as I described above. However, I have not suffered any head injury before like shivia, and I am not disabled like you are. That's what makes solving this issue so enigmatic. There seems to be no common factors, because everybody's situation seems to be different!
So unlike some others here, I don't believe I have any issues with fonts, pulse-width modulation, Windows versions, drivers, temporal dithering, and other suspected causes that I've seen here. Only a small minority of others here seem to describe the issues I'm having with all LED-backlit displays.