I used to be one of those setting everything to dark mode, custom CSS and all, but I am now cured. It was a difficult time as my eyesight was rapidly deteriorating to the point that I thought that I would need to change carers to something not involving computers. I am so thankful that it is over. The source of the problem was that I had been consistently over-prescribed by different optometrists. I don't blame them, but something must be off in how they were trained. To avoid this issue, do not use regular progressive lenses in your eyeglasses. Instead ask for an "intermediate distance" formula optimized for the typical distance between your eye and the computer monitor. In practice this is a depowered formula supposed to be used only for computer used, but I used it all the time. On my next checkup my official formula had decreases confirming that it was too strong in the first place. I know don't have to use dark mode, and my vision is much better in general (I'm in my 50s). And don't over use your phones!!