Stop with the extensions. There's a reason your eyelashes are the length they are. A new study claims a mathematical formula adopted by evolutionary biology offers eyes the perfect amount of protection from the elements.
According to researchers at Georgia Tech, the ideal eyelash length is one-third the width of the eye. And it's not just the human genome that's adopted this perfect formula. Researchers found that 21 other species, in addition to Homo sapiens, utilize the ratio -- including sheep, giraffes and hedgehogs.
In addition to analyzing animal hides from the American Museum of Natural History in New York, scientists constructed a model eye and put it inside a wind tunnel to better understand the reasoning for the dimensions. Researchers varied the eyelash length to see what effects it had on wind turbulence around the eye.
It turns out, anything shorter or longer than standard (one-third the width) length increases the odds of getting dust and debris in the eye.
"Eyelashes form a barrier to control airflow and the rate of evaporation on the surface of the cornea," lead study author Guillermo Amador, a researcher in mechanical engineering at Tech, explained in a press release.
"When eyelashes are shorter than the one-third ratio, they have only a slight effect on the flow," Amador said. "Their effect is more pronounced as they lengthen up until one-third. After that, they start funneling air and dust particles into the eye."
The medium length (again, one-third), on the other hand, reduces air flow just enough to allow water moisture to form a protective layer, shielding the eye from debris and dust.
While the fake eyelashes aren't ideal when they extend eyelashes longer than necessary, they are certainly recommended if a person can't grow their own. Any eyelash is better than none, researchers say.
Additionally, Amador and his colleagues say the newly identified ratio could potentially have industrial application. Eyelash-like protectors could be used to protect solar panels and other lens-like surfaces that exist in dusty environs.
The new study was published this week in the journal Royal Society Interface.