Sometimes micro debris or "microparticles" are interacting with human's (and animals's) eyes:
It can be some types of dust or hair pieces trimmed with a trimmer; I especially mean little particles of matter that can rarely be seen without lots of light and/or common magnifying tools such as magnifying glass (hand lens).
I know that in an healthy person without glaucoma, for example, liquids such as excessive water would be pumped off the eye, but I'm not sure that counts things likes trimmed hair, etc.
How is micro debris cleaned from the eye in unusual cases?
Google searches of:
How does the eye clean itself? How is debris cleaned from the eye? How is micro debris cleaned from the eye in unusual cases?
didn't bring any direct answer on this question besides some data on the eye cleaning itself in blink and while a human sleeps by tears. Also, I learned that humans have three types of eye tears: Basal, Reflex and Emotional; the first two are clearly protective.