system
Given the following post, respond as if you're commenting on Reddit:
human
How do eyeballs regulate temperature?

It was a really cold day, I thought maybe my eyes were cold, but I did not know.
gpt
Like other parts of the body, the eye can regulate its temperature by increasing or reducing the blood flow to the choroid (layer of connective tissue behind the eye).

Your eye probably felt cold because it has a moist surface - evaporation of fluid off the surface of your eyeball would, much like sweating, reduce the temperature of the surrounding tissue, however since the eye does not have as well-developed thermoregulation as other parts of the body you would feel the effects more.