Ideal lash length follows one-third rule

From ABC Science, 25 February 2015:

Long lashes may make your eyes stand out, but researchers have discovered the ideal lash length that protects your eyes from dust and damage.

The study, published today in the Journal of the Royal Society Interface , found that eyelashes of a length around one-third the width of the eye set up a protective zone of still air over the eyeball’s surface.

Lead author Dr David Hu says he began to question the function of eyelashes after spending hours gazing at his newborn daughter’s eyes.

“For a long time there were quite a few hypotheses about what eyelashes were for,” says Hu, associate professor of mechanical engineering and biology at the Georgia Institute of Technology.

Some have suggested they shade the eye from the sun, while others hypothesised that they act as dust catchers for dust falling from above.

“But there’s been no careful study of how they would do these things.”

Hu and colleagues studied the eyelash length of 22 mammals including the red kangaroo, camel, African elephant, giraffe, zebra and chimpanzees.

“We went to the Museum of Natural History in New York City, where they have hundreds of these animal pelts in the basement, and we measured carefully the eyelash length of all these animals,” he says.

“We showed that they followed this pretty strict relationship; that is the lash is about one-third the width of the eye.” Read more.

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