I know how irritating it can be to have your eyes strained by a monitor. Whenever I've had to change jobs/offices I noticed my eyes would start to hurt within a few hours of sitting at the PC. Adjusting both the brightness and contrast always solved that problem.
A little while ago, the lighting above the area where I work dimmed for whatever reason, and I noticed my eyes began to hurt once more. This proved to me that its not just the monitor display settings, which had not changed, but the lighting of the rest of the environment that made the difference. Again, even in this case, adjusting both the brightness and contrast on the PC display relieved the strain on my eyes.
Edit (@FrozenKing replying to your comment below)
Current Display Settings
Standard lighting: Brightness 60, contrast 65
Low lighting: Brightness 65, contrast 55
CURRENT: Brightness 50, contrast 50
low (current) lighting: Brightness 45, contrast 35
Really Low lighting: Brightness 0, contrast 0
If I were to forget what they were or they were reset by accident, I would do:
- check for sense of subtle strain on the eyes while sitting in front of PC
- adjust brightness or contrast down until I got a noticeable improvement in eye strain
- if I don't like the screen display color quality, increase either one of brightness/contrast while ensuring my eyes are not affected.
- keep going back to #1 until I feel no strain on my eyes at all
I think the key is that my eyes are sensitive enough that I don't need to sit in front of a PC for hours before knowing whether the settings are right for me or not. I know immediately. On the other hand, it might be much harder to find the right settings after my eyes have been straining for a very long time.