I’m talking about the dry stuff you find at the corners of your eyes when you wake up in the morning. I sometimes find it sticking to my eyelashes as well. If I get to it before it dries completely, it is a sticky liquid, with the consistency and color of phlegm. It’s not a uniquely human phenomenon. I’ve found the stuff at the corners of my dogs’ eyes and my cats’ eyes (back when I had cats). I recall coming across the medical term for it several years ago, but I can’t find it now.
As long as we’re at it, is it really dried tears? Most people seem to assume so, but I’m not sure.
I can’t find a source for the actual medical term for that crust. My suspicion is that, because it’s not pathological–I mean, you can pretty much just wipe it away–it may not have an official term.
It’s produced by sebaceous glands in your eyelids called the Meibomian glands. These glands produce an oily layer which prevents your tears from evaporating as quickly as they would without it, thus causing you to have to blink quite a bit less. That oily layer–not to mention the lachrimal (tear) layer itself–continues to be produced when you’re asleep. The tears evaporate, but some of the oily layer, as well as salts in your tears, do not evaporate. They mix together to form that crust.
evilbeth, I agree with you. Rheum it is. Another term I’ve heard – my dad told me his parents used to say it – is slam. I have no idea where they got this, but they were Irish. Is slam still extant in Ireland as a synonym for eye-boogers?