I remember reading an article years ago which explained that the reason people get eyestrain from a white background is that the monitor's brightness is set way too high. With high brightness, the monitor acts as a light shining directly at you all day. Instead, you want it to be more like paper- low light emission but still readable due to contrast. At the time, I was using dark mode heavily, but I was still having bad eye strain. I tried lowering the brightness of the monitor, and the problem went away. Since then, I've only used light mode with a low brightness setting of 30 out of 100. I encourage people to experiment with it. Note, if you are not used to low brightness, the monitor will look incredibly dim. But your eyes will adjust quickly- mine only took a few minutes.