Exactly right, which is why I adjust my monitor settings down if I stay late at the computer. Do do it in steps, and the adapted eye can go down even farther than "xrandr --output HDMI-0 --brightness 0.05 --gamma 2.0:1.0:0.5" and still see quite well... ;-) Also, for people who read from a tablet or phone in bed, use software that supports a night mode. Set background color to black and font color to dark amber. Then gradually shift down overall brightness. Personally, I use "Cool Reader", which is really good for that, as it lets you adjust brightness just by sliding up/down on the left screen border.