There seems to be a LOT of confusion about how frontlight works, so i'll try to explain it:
There's a number of LEDs at the bottom of the screen, which, when traveling through a layer on top of the e-ink screen, will light up that screen.
This happens by diffusing the light. diffusing means to bounce or scatter the light in other directions than just straight ahead (if it were to go straight, you would only see light at the bottom of the screen, and at the very top, because of the edge)
the reason we see these light spots, is because the layer is bend in those places, due to pressure.
There are no lights at the sides of the screen:
thanks for resizing, issybird. I didn't know how to do that.