So I figured we should probably keep things a little light hearted today. The last time I wrote, I talked about various eye cancers. This time…let’s talk about the ‘crusties’ that end up in the corner of your eyes when you wake up in the morning. Sometimes it’s sort of thick and gummy; sometimes it’s hard and sharp like thorns. So what is that stuff anyway?

First, I think it’s important to understand the role that tears play to our eyes. The very front surface of the eye gets nutrients and oxygen from our tears. The oxygen dissolves out of the air into the tears, and then gets absorbed by the cells on the front of the eye. This is how our cornea is able to be clear. If it could not get oxygen from the air, it would have to have blood vessels to nourish it.

The tear film on the front of the eye has three different layers. The layer closest to the eye is mucus. The mucus sticks to the front skin cells of the eye and coat very well. We have special glands in our eyelids and on the conjunctiva that produce this mucus. The main layer of the tears is the watery layer which comes from our lacrimal gland, located underneath the outside portion of the upper eyelid. Lastly, on the very surface of our tears, is an oil layer. The oils are produced by long test-tube shaped glands right behind our eyelashes. The oily layer spreads nicely on top of the tears and prevents them from evaporating too quickly. Believe it or not, this is the simplified version of our tears. Some eye researchers spend their entire careers studying the tear film…you laugh, but I’m not joking. All of our tears drain through very tiny little ducts located within our upper and lower eyelids…nearest the nose. If you look closely in the mirror and pull down your lower eyelid, you will see a hole near the inside corner. This duct drains tears down the back of the nose and then the back of your throat.

So what is ‘sleep’ anyway? Simply put, it’s dried up tears. At night, the drainage ducts get blocked because our eyes are closed. The tears that you produce over night will slide towards the inner corner of your eye to drain, but they can’t get down the ducts. The trapped tears, which are made of mucus, water, and oil begin to dry up. And what evaporates first? The water. And once the water is gone you are left with just oil and mucus, which gums together sort of like snot (sorry, it’s true). As the gummy snotty tears dry up, it leaves ‘sleep’ in the corner of your eyes. Could be why some people call them ‘eye boogers.’