I understand its useability very well. Traditionnal monitors are called CRT, meaning Cathode Ray Tube. They have an emitter from which electromagnetic rays are projected to the front, the screen. Of course, many penetrate, and interfere with your body, and eyes. If you're sensitive to it, too much putering takes away loads of energy, and people tend to be stressed, more agressive and exhausted. It can even lead to feelings of depression etc. Yetthis screen does change what you see as is prevents certain rays to come through.
Therefore, if you can afford it, the new flatscreens are much better as they ar based on different light generating principles. And they can be perfectly calibrated. Of course there's always a difference in quality, and also guarantee. Their weak point is that they are impossible to repair. So if you go for one, do stress on this point, and also on the contrast, the angle of view and the refreshing rate. The latter is very important for the gamers amongst us..
Why do you need to use that anyway?