system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how does sleep cure bloodshot eyes?
gpt
Optician here. Your eyes have a tear film on the surface that keeps them hydrated and oxidized. Throughout the day, your eyes get dry and bloodshot from heat, cold, wind, smoke, pollution, allergies, etc. When you sleep, your closed eyelids allow your tear film to rehydrate your cornea for several hours and provide plenty of oxygen to your tired blood vessels. Your entire body goes through restorative processes in your sleep, and your eyes do too.