The Jesus PC Illusion

How does the Jesus optical illusion work?

By staring at the illusion for so long in one place, the light from your monitor temporarily makes an impression within your eye on the light receptors. When you look up and blink at the wall or ceiling, the image becomes more clearly visible to you in a negative form. Since it was a negative image to begin with, you have reversed the image back into a positive.

To prove this theory, I opened the image in a photo editing program and selected "invert colors" from the drop down menu...
                                   Before                                                                      After