Eyelids are the superthin pieces of movable skin over our eyes. Even though we rarely notice it, we’re using our eyelids all the time. The main thing they do is blink. A human adult blinks up to 1,200 times an hour!
Every time you blink, your eyelids wipe away dust and other tiny bits of muck. They spread tears across your eyeballs to keep them moist. And if a light is too bright, or something comes too close, those trusty eyelids will snap shut to protect your delicate eyes.
Many species of geckos don’t have these flaps of skin to protect their eyes. Instead, see-through coverings called spectacles help keep their eyes safe. They’re like windows over each eye—windows that they can’t open or close.
Without an eyelid blinking to clean it, a gecko’s spectacle collects a lot of grime from the environment. And when that spectacle gets too filthy, the gecko’s long, sticky tongue comes to the rescue. It quickly flicks out of the gecko’s mouth and, with a little squelch, licks the grubby eyeball. This wet lick coats the eye with saliva—and slurps off all the gunk that has collected there. Now the eyeball is as clean as a whistle!
So next time you find yourself face-to-face with a crested gecko, don’t be grossed out by its wandering tongue. The gecko isn’t being rude, and it’s not getting ready to enjoy a tasty eyeball snack. It’s just doing what you and I do thousands of times every day—cleaning its eyeball.
