Coma Niddy explains why do our eyes hurt when we are used to dark and then we enter in a bright lit chamber. It is because of our rod cells, from our retina. In there, a substance rhodopsin is responsible of human night vision, and it will send strong signals to the brain if we simply get into a room full of light without proper preparation.
Also called visual purple, the rhodopsin, needs time to build up to its full capacity, about 30 minutes. So, when you come to a bright lit room you better get used to the light or else face the pain in the eyes. Science has once again explained, to a certain degree, why our eyes hurt that much when we fed them too much light all at once.
Via [Coma Niddy].