I had the exact asame issue with this monitor, and an LG monitor. The only solution I could find was to download a free application called Dimmer. Once it's installed, you'll see a little light bulb icon in the menu bar, click it, and move the brightness down.
It looks to me like the brightness is way too high, even on the lowest settings. Either that, or a problem with gamma settings.
This is exactly what I did. However the screen looks awful. I am not 100% sure whether the Size to Screen Fit was set but I think it is by default.
Jasmus - I will have a look but other than the brightness the fonts are not clear and would hurt ones eyes if you had to use it for long periods of time.