Women often go to great lengths (pun intended) to gain the most perfect, curly, long eyelashes using mascara, fake eyelashes, and even treatments like Latisse. Now scientists have revealed the perfect lash length, proving that more isn't always better.

According to a study published in the Journal of the Royal Society Interface, the best length for eyelashes is one-third the width of their eye. Anything shorter or longer increases airflow around the eye and leads to more dust hitting the surface.

Hollywood starlets might use many devices to seem more easy on the eyes, but it appears that nature got things right. Researchers found that 22 species of mammals - including humans, hedgehogs and giraffes, but excluding elephants - follow the one-third rule.

"Eyelashes form a barrier to control airflow and the rate of evaporation on the surface of the cornea," lead author Guillermo Amador, from the Georgia Institute of Technology, said in a news release. "When eyelashes are shorter than the one-third ratio, they have only a slight effect on the flow. Their effect is more pronounced as they lengthen up until one-third. After that, they start funneling air and dust particles into the eye."

So how did scientists figure out what constitutes the perfect eyelashes? They built a wind tunnel about two feet tall, complete with a makeshift eye, of course.

A 4-millimeter deep, 20-millimeter diameter aluminum dish represented the cornea. It sat on top of an acrylic plate, which imitated the rest of the human face. Mesh surrounded the dish to serve as the eyelashes. During the study, they changed the mesh length while paying attention to evaporation and particle deposition.

"As short lashes grew longer, they reduced air flow, creating a layer of slow-moving air above the cornea," explained researcher David Hu. "This kept the eye moist for a longer time and kept particles away. The majority of air essentially hit the eyelashes and rolled away from the eye."

However, longer lashes extended further into the airflow and created a cylinder, leading to faster evaporation.

"This is why long, elegant, fake eyelashes aren't ideal," said Amador. "They may look good, but they're not the best thing for the health of your eyes."

Researchers hope their findings can one day lead to eyelash-inspired filaments to protect solar panels, photographic sensors, or autonomous robots in dusty environments.

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