system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - What makes the whites of your eyes greyish / bloodshot when you're super tired?

I haven't slept well in months (cos baby). The whites of my eyes haven't been bright white for a long time now - they're perpetually greyish and feel really rough / sandpapery. Why does being tired make them discoloured? Also, by most evenings my eyes are bloodshot. What makes this happen and why aren't they bloodshot all the time given how knackered I am?
gpt
Your tears have a particular mixture of water, oils, proteins, sugars, and salts to help moisturize and protect the surface of the eye.

As you stay awake longer, the quality of your tears degrades because your tear ducts also get tired. This causes your eyes to dry out easier, causing irritation and redness. It also makes you want to rub you eyes to help smear the tears you have left.

Your tear ducts need shut eye time to recharge and refresh it's production of tears. If you don't let your body sleep, your tear ducts are not able to produce good quality tears. You can substitute with artificial tears (different from the eye drops with medication to reduce redness) but ideally, you should restore your natural tear production.