David Lu and colleagues from the Georgia Institute of Technology studied samples from the American Museum of Natural History in New York, and found this eyelash to eye length ratio in 22 species of mammals.
The researchers noted that lashes of the optimum length delivered several advantages including minimising dust particles and evaporation of the eye surface. Having built a mini wind tunnel to test the aerodynamic properties of different models of lash lengths, they discovered that lash length also re-directed the airflow.
While longer lashes directed the flow of air to the ocular surface, increasing evaporation, and increasing the likelihood of the eye drying out, shorter eyelashes did not stop the flow of air. Instead they created a ‘stagnation zone’ above the eye’s surface.
The authors suggested that the optimum length minimised dust particles and evaporation of the eye surface. They suggest that ‘eyelash-inspired protection’ could be used to protect optical sensors.