What are those black spots in the whites of people's eyes?

Before I came to Taiwan, I’d never seen these before. I’m talking about the little inky patches, perhaps 1-2mm in diameter, in the whites of their eyes. They’re not that common, but common enough that I encounter someone with them every few months. Today, I met a kid who had three in one eye.



Seriously? Do they have any effects other than the aesthetic? For instance, are they related to anything else, such as the incidences or susceptibility to certain conditions or illnesses?

Apparently most are congenital and harmless.