Do you use a Mac laptop at night? Is your lighting usually dimmer than the screen? Do you turn the screen brightness down?
If you answered yes to any of these, you might want to try Flux. Flux changes the color of your screen to a warm yellow at night. It looks weird and broken at first, but after using it for a month, I can attest that it does reduce eyestrain.
If you are watching a movie or working on something color sensitive, you can easily disable or quit Flux via it’s menubar item. But for the rest of the time spent surfing the web, I have found that my eyes are a lot less tired after several hours of being on the computer.