RedScreen is an utility that adjusts your screen settings for night viewing. The application can help you work on your computer with low light in two different ways. First, and the simplest way, is to darken the screen. It can effectively darken the screen more than you can do it using the built-in brightness controls. The second way in which this app can help is where it gets its name from (RedScreen). It applies a red filter to your screen, while also reducing the brightness of it and applying some dimming. This produces very little light and apparently, it will not make your eyes hurt when looking at your screen at night.
When you first launch the application, you will be given the option to choose one of the two methods that I described above, but you can change this from the settings menu, and even adjust the degree of redness, dimming and backlight used. RedScreen can disable or replace your screensaver. There is a checkbox that reads "Invert" which makes the background black with red touches. This works better for me than the red filter.
I tried RedScreen during the day, so I can't say whether it will help at night or not. It is free, so give it a try.