F.lux Changes Your Screen Brightness by Time of Day: "One of our favorite tools" - Lifehacker
"One of our favorite tools to protect your eyes" - Lifehacker
I've been using this for a few weeks, it makes the computer display a LOT easier on the eyes.
It changes the color temperature of the display based on the time of day.
Their reasoning is that blue light at night can cause insomnia, so they change the color temperature of the display from "cold" in the day to "warm" in the evening.
I browse on the laptop while watching TV at night in the dark. Web pages are mostly white, making them much brighter than the tv screen, even with the laptop brightness turned all the way down. The bright white web pages also ruin night vision. Set the night color temperature to "dim incandescent" or lower and problem solved.
It's free, and they have versions for windows, mac, android, iphone, etc.
They also point out that most displays are "colder" than natural daylight, so they let you set the daytime color temperature to a warmer value.
They also make it easy to turn off temporarily for photographers etc.