Most of us think of tears as a human phenomenon, part of the complex fabric of human emotion. But they’re not just for crying: All vertebrates, even reptiles and birds, have tears, which are critical for maintaining healthy eyesight.

Now, a new study, published this week in the journal Frontiers in Veterinary Science, reveals that non-human animals’ tears are not so different from our own. The chemical similarities are so great, in fact, that the composition of other species’ tears—and how they’re adapted to their environments—may provide insights into better treatments for human eye disease.

Previously, scientists had studied closely only the tears of a handful of mammals, including humans, dogs, horses, camels, and monkeys. In the new study, Brazilian veterinarians