I don't understand how one can make a monitor "safer", especially in the era of LCD screens with no flicker.
The largest component of eye strain is the brightness of the screen, make sure you have that set properly, i generally have mine cranked all the way down, also make sure that your screens are at the right height so your neck isn't in a bad position, and that you are far enough back from the screen that you don't have to move your eyes too much to see everything on the screen.
There isn't going to be a magical filter to make them magically never cause eye strain, staring into a light source for extended periods of time will always cause eye strain.