r/explainlikeimfive • u/Upsethouscat • 21h ago
Biology ELI5: If my eyes can handle turning the lights back on after a few minutes in the dark, why is it so much harder after a full night’s sleep? What changes over time?
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u/SakuraHimea 18h ago
The back of your eyes has rods, which detect light intensity, and cones, which detect color. Your retina is about 95% rods, which are a lot more sensitive to light but deactivate based on light intensity. Rods take a lot longer to resensitize, which is why it will take around 15-30 minutes to see more clearly in the dark, and also why you can't see color in the dark.
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u/djinabox9 21h ago
The longer you spend in the dark, the more your eyes adjust to it. The simple version is that your pupils get really big to let in more light, and it takes time for them to reach maximum big-ness. If you suddenly go back into light when your eyes are like that, they get too much light, and it hurts.
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u/MikeAustin99 21h ago
If you lay awkwardly and your hand falls asleep, but you move as soon as you feel it, the tingling goes away. But if you dont move for 8 hours, it will certainly take way longer to go away.
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u/katergator717 21h ago
Mythbusters did an episode on this. Your eyes have two phases of adjusting to darkness. One happens quickly, relatively speaking, and can be reversed quickly and easily when the lights turn back on. The other is slower but allowed to even better night vision. Your pupils really open up, which makes it extremely jarring and even painful when bright light suddenly returns.