You've got a body part you've never heard of—and neither had anyone else, until now. Scientists have discovered a sixth layer in the eye's cornea, which was previously believed to have just five layers. The new layer, which researcher Harminder Dua has dubbed Dua's layer, is only 15 microns thick, Popular Science reports. For comparison, Discovery News reports the layer is "smaller than beach sand and mist"; the entire cornea measures 550 microns thick. Still, Science Daily describes it as "incredibly tough and strong."
But the find could have big implications for health: A tear in the layer is likely the cause of a disorder called corneal hydrops, in which fluid builds up in the area. The discovery of the layer could lead to better surgery for related problems. "This is a major discovery that will mean that ophthalmology textbooks will literally need to be re-written," Dua says.