I first experienced eye strain about 2 years ago from a crappy laptop display that uses LED backlighting, PWM, 6-bit per channel color, and has a pretty noticable blue tint to the screen. That was a switch from a long line of CCFL backlit laptops and CRT monitors, which never gave me eye strain.
My initial symptoms were eye discomfort (like pressure on my eyes, or mild ache), which progressed to a sort of pinching in the center of my brow and more severe eye discomfort, difficulty keeping my eyes focused when reading, and eventually feeling nauseas. The only thing that helped was to get away from displays, which I did to a large degree for some months.
When I first experience eye strain a couple of years ago, I was using a computer heavily, using the command line on linux, reading electronic books (mostly pdf's), reading lots of online articles, and programming for long hours. I was reading from a computer all day, every day, indoors and outdoors.
The factors which I think contributed to my eye strain are glare (computer use outdoors) and a bad quality display. I can't say for sure which qualities of the display were contributing factors. I can only mention what helps. Full brightness, f.lux set at around 3200 or warmer, avoiding glare, and not spending too much time reading from a display.
Since that initial bout of eye strain, I have never fully recovered and I doubt that I will. I'm pretty certain that my eyes were permanently damaged in some way. Every time that I use a display, I have to be conscious of my eye discomfort or else it will get out of hand.
Also, thinking back on my personal vision history, as a kid I preferred reading books in low light. My parents would tell me not to do it, but it felt comfortable to me. I have always been somewhat nearsighted, and I think that I have always had a sensitivity to bright light. When driving, the glare from headlights and streetlamps at night has always been a bit of a problem, especially after a rain.
So I think that in all, my own eye strain (likely damage) has been due to a mix of factors: disposition of light sensitivity, crappy display, outdoor glare, and too much time reading from a display.
What sucks is that my eyes seem to need more light now for even reading from paper, but I have to watch even the glare on paper. In other words, my eyes seem to have a much narrower comfort zone between too much or too little light. And my eyes are now very susceptible to blur, either from not so great font rendering or from motion. For example, I can hardly stand to read from pdf's anymore because the rendering is too blurry for every pdf reader, except for Firefox. And my eyes feel slow to refocus from one document to the next. At work, I'm staring into lines of text entries on both paper and displays, and I can easily perceive the slowness of my eyes refocusing.
I guess that's my story.
Also worth mentioning. I have discussed this issue with a young family member who is attending university, and she says that she is also experiencing eye discomfort from displays, mostly when she is intensely concentrating for long periods when reading from a display, as when doing math, not when merely reading articles, for example. For myself, eye discomfort is at it's worst when programming, where I am also intensely concentrating for long periods.
If anything here rings a bell with anyone here, or if you have found ways to deal with, what seems like permanent eye strain, I would like to hear from you. Unfortunately, I only have a few suggestions of my own:
If a display is causing eye discomfort within a short amount of time, get away from it immediately.
Do what you can to spend less time in front of a display.
Avoid glare like the plague.
Avoid blurry font rendering like the plague.
Do what you can to minimize blue light from a display.
I'm still on the fence on the effects of PWM.