Killing the demodex both helps with dry eyes apparently, and is supposed to reduce infection on eyelid margin (which I'd had a few times).
(And we had the "yeah, but by changing two variables at once (vit D and ivermectin) it means we'll never know which helped, but since the ivermectin is one-time and the vit D has other benefits, who cares?" discussion in the office, for about 30 seconds.)
All adult humans have eyelash mites. "Demodex" is the name of the mite, not the mite-killer.
Having never heard of this before I am now terrified. [1] :-)