The ciliary muscles and suspensory ligaments around the lens are under more strain because they're not being worked in a way that is ideal, particularly you're spending long periods of time in front of the screen at that resolution.
You're not necessarily going to 'feel' it, but over a period of years, the muscles and ligament degenerate and become less flexible. If you're young, you probably won't notice it until its too late, and its even more of a risk factor if there's any family history of shortsightedness or astigmatism.