With multi-monitor setups no longer a rarity, users are sitting from front of a great amount of emanating, bright light. But oftentimes, especially in mix and match dual+ monitor setups, one screen is brighter than the other, which can result in tired eyes. Here's a simple trick to improve calibrating a multitude of screens...
Oftentimes, people will purchase a new laptop to complement a desktop at home (though this is changing, with many now opting for a laptop only household). If you've got bright LED backlighting in your laptop, and your desktop monitor is somewhat older and doesn't have LEDs, odds are that your laptop's screen will be significantly outshine the older monitor. We've experienced a similar issue with the brightness level of our laptop, as our 2006 22" computer screen is noticeably dimmer than our LED illuminated MacBook Pro.
The difference in brightness between monitors can cause eyestrain, so it's best to dial down the brightness of your laptop to match the glow of your other computer screen(s); same applies if you get a newer computer screen.
Slightly dimmed monitor settings are also better when reading from a screen (it's partially one of the reasons why e-ink displays are so nice for e-readers). We tend to dial the brightness to the max while working, but when we read, we dial it down to almost the minimum. It makes the text easier to read and is less strenuous for your eyesight.
If you're looking for a more automated solution, we'd recommend trying out f.lux, an extension for Windows, OS X and Linux users that adjusts the color of your computer's display in relation to the time of day, warm at night and like sunlight during the day.