Why Do We Have Eyelashes? New Study Says It’s to Keep Our Eyes Moist
Why do we have eyelashes? The answer seems simple: the thick hairs at the end of the eyelids exist only to prevent invading particles from falling on the eyeballs.
And, in fact, this is the assumption of many scientists. It explains why camels have evolved into long eyelashes that can linger in the dusty desert, and why in contrast, our domestic pets are strong.
But the facts show that our eyelashes may also help in other ways: to prevent the surface of the eyes from drying out. It can make people better understand why some people have long-term dry eyes, and it can even help us make better false eyelashes.
A team of chemical engineers from Soochow University in China analyzed evaporation rates of liquid on eyes with different eyelash lengths. Not only did eyelashes help retain crucial moisture, but researchers confirmed results from a 2015 study that showed there may even be an optimal eyelash length for keeping the eye’s surface moist.
Longer Isn’t Better
Though the study was done on computer models, a study author and the deputy head of the School of Chemical and Environmental Engineering at Soochow, says via email that it’s the most geometrically accurate eyeball model yet. The team had to take into account differing lengths of the top and bottom eyelashes, curvature of the eye’s surface and position of layered lashes, among other factors.
Their query into eyelashes’ moisture-preserving properties was inspired by a study from 2015, which concluded that eyelashes help divert wind from the ocular surface.
Like the 2015 study, It turns out that some eyelashes were more efficient in blocking wind than others. The authors reported that the optimal eyelash length for moisture retention is about 15 to 30 percent of the eye’s width.
So, if you have long lashes and find yourself often with dry eyes, the reason may lie just outside your field of vision.
Though eyelashes take most of the credit for keeping our eye surface moist, they aren’t doing the work on their own.It is a complex problem. The thickness and distribution of eyelashes and the curvature of an eyeball also influence the evaporation of moisture.