TEARS REVEAL SOME OF THEIR DEEPEST SECRETS TO RESEARCHERS

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COLUMBUS , Ohio – It's no secret why we shed tears. But exactly what our tears are made of has remained a mystery to scientists.

A new study sheds some light on the complex design of tears. What we think of as tears, scientists call tear film, which is made up of three distinct, microscopic layers. The middle, watery layer – what we normally think of as tears when we cry – is sandwiched between a layer of mucus and an outer layer of fatty, oily substances collectively called meibum.

It's in this outer layer that researchers describe, for the first time, a new class of lipids – a type of fat – that make up part of the film. They also identified one of these lipids, oleamide, which had not been known to be a part of tears before.

With each blink, meibum spreads over the surface of the eye. It keeps the watery middle layer in place, ensuring that our eyes stay moist.

Finding these lipids may help scientists better understand the causes of eye-related disorders such as dry eye disease, which affects anywhere from 12 to 14 million Americans, said Kelly Nichols, the study's lead author and an assistant professor of optometry at Ohio State University.

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