Why do eyes turn red?



Sometimes they just turn real red and I can see the nerves but at other times I cannot. Why does this happen?

In: Biology

your eyes are filled with a lot of tiny veins (capilaries). they are almost invisible most of the time. But when your eyes are irritated, when you consume a vasodilator (a molecule that makes your sphincters open) molecule or when you are forcing the focus on something “hard” to focus on, your eyes needs/have more blood, making your veins bigger and you can see them.

You cannot see the optical nerve in your own eyes (and it would be a cause for concern if you did). If your eyes are red that means the capillaries that provide blood to it are swollen, either due to inflammation, or just irritation. Your eye muscles could be strained from working too hard, or there’s a piece of dust that the eye is working extra hard to remove by blinking, tearing and such.