Chrome: Many websites are almost blindingly bright, with glaringly white backgrounds that could cause eyestrain. Deluminate is an extension that lets you dim or invert the luminance of pages in your browser so they're easier to read.
The extension has a number of settings as well as keyboard shortcuts to turn Deluminate on or off for any site you're on. You can simply dim a page so that it's grey instead of white, or you can invert the luminance, as shown above. You can also control how images are treated in the tweak.
So far I've been using it on the lowest dim setting and my eyeballs are happier.
Deluminate [Chrome Web Store]