eyes

[Mao]

IMO, it's not the brightness that gives the trouble. It's the working distance of your eyes to the monitor. You see, the lenses of our eyes are just like the lens of a camera, they adapt to adjust the focus. They bend (concave or convex) to adapt to the image we try to focus on. Now, when you use your computer way too much, your eyes get accustomed to focusing on something near (just like when reading), so they have a difficult time adjusting to focus on something much further. If you do use the computer a lot, or read heavily, myopia (nearsightedness) is inevitable. Just take in a lot of vitamin A and try to not read or use the computer too much. I think there are glasses or lenses though that provide the correction of your lenses through time.