Researchers determined the exact length eyelashes should be in order to protect the eyes from harmful dust and debris.
The recent study found that at least 22 species of mammals have eyelashes that are one-third the width of the eyeball, and any length shorter or longer than that did not effectively protect the eye, Georgia Institute of Technology reported.
"Eyelashes form a barrier to control airflow and the rate of evaporation on the surface of the cornea," said Guillermo Amador, a Georgia Tech Ph.D. candidate in the George W. Woodruff School of Mechanical Engineering who authored the study. "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."
To make their findings, a research team built a wind tunnel to simulate air flow on a model of a human eye consisting of a 4-millimeter deep, 20-millimeter diameter aluminum dish atop an aluminum plate (to mimic the face) and surrounded by eyelash-like mesh. By varying the length of the mesh, researchers discovered the ideal eyelash ration.
"As short lashes grew longer, they reduced air flow, creating a layer of slow-moving air above the cornea," said Assistant Professor 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."
The team found the opposite was true for longer eyelashes, which can extend further into airflow and form a cylinder. This causes the air molecules to be channeled toward the eye, leading to faster evaporation.
"This is why long, elegant, fake eyelashes aren't ideal," Amador said. "They may look good, but they're not the best thing for the health of your eyes."
The findings could be used to create eyelash-like filaments that protect solar panels as well as photographic sensors in robots that work in dusty environments.
The research was published in a recent edition of the Journal of the Royal Society Interface.
