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What Are Eye Boogers?

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Channel: BrainStuff - HowStuffWorks
Categories: Biology   |   Health   |   Science  
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The gunk builds up at the inner corners of our eyes is residue of the stuff the coats and protects our eyeballs all the time. Learn what it’s made of and why it turns to sand overnight.

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Hi BrainStuff, Cristen here. Today’s question is “What are eye boogers?” If you’ve ever had to wipe gunk out of the corners of your eyes, it’s not because you were visited by the Sandman or a magical mucus fairy. Nope! We live in a cruelly mundane universe. I’m sorry if I’m the first to break it to you.

Eye boogers are a buildup of the “precorneal” or “basal” tear film that coats and protects your eyes -- plus any foreign particles it catches.

This tear film is just 3 micrometers thick, which is less than half the diameter of a red blood cell, but it’s made up of 3 components: the mucin, the aqueous, and the lipid.

The aqueous component is the operative one: It nourishes, lubricates, and flushes your eyes’ cells. It also smoothes over the microscopic lumps and bumps on the surface of your eyes, creating a smooth lens that optimizes light transfer into your retina.

The other two components are a support system for the aqueous one: The mucin component underneath allows it to temporarily stick to your eyes. Mucins are the proteins that make mucus slimy.

And the lipid component outside holds it in place, so that you’re not just crying constantly like you’ve got Moulin Rouge playing on loop. Without the lipid layer, our tear film would drip right off of our eyeballs.

But how do these components become eye boogers, and why do they accumulate in the inner corners of your eyes? I’ll tell ya.

When you blink, your entire eyelid doesn’t close simultaneously. It shuts like a meaty clapperboard, from the outer corners of your eyes inward toward your nose. Your tear film gets pushed along by the motion.

Upon reaching the inner corner of your eye, most of the film drains out through the tear ducts, which empty into your nasal cavity. But some of the film – the mucins, oils, and debris – can clump together and get stuck.

When enough of that builds up, it forms the goop known as eye boogers. And when it accumulates and dries overnight because you’re not blinking it away, it forms the crusty gunk known as sleep or sand.


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