system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is actually happened when your eyes “adjust” to light?

Examples: walking out of a movie theater during the day - when someone opens the blinds in a dark room.
gpt
Two things happen: the fast response and the slow response. 

**Fast response to light:**

Your iris dilates and makes your pupil (the hole in your eye through which light enters) larger so more light can get in. 

**Slow response to light:**

When it’s dark, a chemical referred to as “visual purple” (I think its technical name is rhodopsin) gets secreted to your retina which makes the nerves more likely to fire when any photon hits it. That takes a lot of time to fade out of your eyes when it’s bright which explains why it takes so long for your eyes to adjust. 

**Fun factoid:**

“Some historians” believe pirates are associated with eye patches not because of eye injuries but because of the need to rapidly go between the extreme Caribbean sun and the extreme dark below decks. Your eyes can adjust to light independently. So a theory is that pirates would switch the patch from one eye to the other to allow them to see well both above and below deck when fighting for control of a ship.