Because by blurring your vision, you are reducing the amount of information that is being received by your visual cortex. This goes to
show, yet again, that DP is to
a large extent dependent on your environment and how
you experience/interact with it. It simply proves, yet again that DP is not a mental condition that is somehow beyond your control.
With DP, it can seem very tempting to stay in bed all day, not shower etc every day, to just let yourself go a bit.