The true purpose of eyelashes? Controlling airflow around the eye. Researchers at Georgia Institute of Technology measured lash length and eye width in 22 preserved mammals ranging in size from hedgehogs to giraffes. In all species, lash length was about one-third eye width, suggesting they had evolved to be a particular size relative to the eye. The researchers made artificial eyes, attaching synthetic lashes to small water-filled aluminium caps and monitoring the “eyes” water loss and particle deposition by 50%, as they trap a protective layer of air on top of the eye. Lashes that are too long no longer trap air and instead funnel airflow onto the eye, likely increasing evaporation and particle deposition.
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