I much prefer dark backgrounds also, but just not practical all the time. I have to deal with sensitivity to bright lights, etc... Can't hardly go outside on a sunny day without sunglasses, at least not if I want to be able to open my eyes.
You really should be dealing with this by adjusting the brightness and contrast of the monitor though. I am on maybe 5-8 screens in a given day and must adjust these settings several times. When I'm on the same computer screen for a day, it gets adjusted several times that day.
If the screen hurts to look at or causes you to squint, it's time to crank that brightness down to an acceptable level.