There are fats in the tears you cry

 Tears are not just water and salt, say researchers at Ohio State University

The reason for crying is not a scientific secret - but what exactly tears are made of remains a mystery to this day.

 New research sheds some light on the complex design of tears. What we call tears, to scientists it is called the tear film, made of three distinguishable microscopic layers. The middle watery layer - which we refer to as the layer of tears that break out when we cry is sandwiched between a layer of mucus and an outer layer of oily material of various types collectively known as meibom.

In the outer layer, the scientists located for the first time a new type of lipids - fats - which are part of the film. They also identified one of these lipids - olamide, which was not known until now to be included in the tear material.

With each blink, meibomian spreads over the entire surface of the eye. It keeps the middle aqueous layer in place, and ensures that our eyes stay moist. Finding these lipids may help scientists better understand the cause of eye-related disorders such as dry eye, which affects 12-14 million Americans, says Kelly Nichols, the project's principal investigator and professor of optometry at Ohio State University. "The absence of components in the tear layer may manifest itself in disorders related to the eye, including dry eye," she said. "The amount of olamide and other lipids in the tear layer may be related to these disorders."

Dry eye is not a single disease but a collection of disturbing symptoms that include microscopic damage to the front of the eye, the eye may also hurt, a feeling of general dryness or a massive leakage of tears. The researchers reported their findings in the current issue of the journal Investigative Ophthalmology and Visual Science.

For the Ohio State University press release on the Science Daily website