I have a character whose eye whites are bright red, and I'd like to make some attempt to justify why.
This character's species has eyes that generally become bloodshot in the same way and under the same conditions as humans', but they are alien, so feel free to take liberties with the biology. The actual appearance doesn't have to be bright red, but should at least be on par with a bad case of pink eye.
It's okay (even encouraged) for the underlying condition to cause other symptoms, and it can even be medically serious, but the eyes should look normal other than the color. Most importantly, the red eyes should be constant or near-constant for years, and none of the other symptoms should point toward a treatment that causes them to go away. (Anything more advanced than eye drops would be obtainable but discouraged in this character's society, so just about anything can be justified as treatable or not treatable as needed.)
If it helps, they are amphibious and spend a lot of time in saltwater, but any explanation using this fact would have to adequately explain why this character alone is affected.
Here's an example of what I found when I searched for real conditions—everything notably short-term except, like, hay fever.
Thanks to anyone who takes the time to help.