A number of conditions can cause an increase in the production of rheum in the eye.
From the en.wikipedia.org
Rheum or prior MA experience preferred.
From the jobview.monster.com
Rheum from the eyes is particularly common.
From the en.wikipedia.org
In the waking individual, blinking of the eyelid causes rheum to be washed away with tears via the nasolacrimal duct.
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The presence of pus in an instance of heavy rheum buildup can indicate dry eye or conjunctivitis, among other infections.
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There was plenty of rheum at the top.
From the time.com
Dried rheum is in common usage called eye gunk, sleepydust, sleep, sleepys, sleepers, eye goop, eye crud, eye crust, eye bogeys, eye boogers, and others.
From the en.wikipedia.org
The absence of this action during sleep, however, results in a small amount of dry rheum accumulating in corners of the eye, most notably in children.
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This causes epiphora, that is, with non-patent nasolacrimal ducts, tears have no egress from the body and rheum is released onto surrounding skin.
From the en.wikipedia.org
In the case of allergic conjunctivitis, the buildup of rheum can be considerable, many times preventing the sufferer opening the eye upon waking without prior cleansing of the eye area.