Rhodopsin is a biological pigment in photoreceptor cells of the retina. It is the primary pigment found in rod photoreceptors.
There are about ~10⁷ rhodopsin molecules in each rod. And ~120×10⁶ rods in a typical eye. (And 5–6e6 cones.) When a few hundred “unphotobleached” rhodopsins interact with light, they become “photobleached”, open up, and that changes the shape of the rod cell. If the rod cell gets big enough, it is more likely to send a glutamate signal “down the line”.
Photoreceptors hyperpolarise to light. Therefore, gluatamate is released when there is a decrease in illumination.
Also your body replaces rods over time.
About 45 minutes after photobleaching, all the rhodopsin proteins will have returned to their closed shape.