"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 funnelling air and dust particles into the eye," Amador said. Amador and the research team led by Assistant Professor David Hu, sent a student to the American Museum of Natural History in New York in 2012 to measure eyes and eyelashes of various animals.