We have all heard the expression: “Those are crocodile tears.” It’s usually said derisively in reference to a pointless show of faked emotion. But researchers studying real tear production in the animal world believe the tears they shed could also shed light on how to treat dry eye and other vision problems in humans.
A team of veterinary researchers in Brazil have collected and compared tear samples from scores of animals, including caimans (a relative of the crocodile), tortoises and turtles; birds such as owls, hawks and parrots; and mammals, including dogs, horses and, of course, humans.
Why We Cry
For you and me, tears have a few jobs. Yes, crying conveys strong emotions like sadness and extreme joy. However, the most important function of our tears is to keep the eye nourished and lubricated so they stay healthy, and to help clear away dust and debris. We blink an average of 15 times per minute to distribute those tears across the cornea so they can do their job(s). Our eyes have adapted to human environments and animal eyes have as well, in fascinating ways.
By comparison, the caiman only needs to blink every couple of hours. (To be fair, they have three sets of eyelids to our one.) When researchers examined the dried tears, they noticed thicker crystal lattices – the geometric structure that forms when the water, minerals, proteins and fats in the tears dry – which could indicate a more stable tear composition.
Like caimans’ and homo sapiens’ tears, other tears examined in the study differed according to the animal’s habitat. Land animals constantly produce watery, refreshing tears. By contrast, the loggerhead turtle’s thick, syrupy tears appear custom-made to withstand contact with seawater. Some invertebrates, like spiders, don’t produce tears at all; they clear debris from their eyes with the hairs on their legs.
We don’t expect to adopt the spider’s eye care methods anytime soon, but the discoveries about tear production in vertebrates, birds and reptiles could someday yield knowledge that helps us better adapt our eyes to an ever-changing environment.
The team at Matossian Eye Associates is highly experienced in the treatment of dry eye syndrome. Call us at (800) 708-8800 to schedule an exam, or request an appointment through MatossianEye.com.