What Do Snakes Have Instead of Eyelids?

Snakes are interesting animals with equally interesting anatomy. One of the snakes’ most interesting aspects is that they don’t have eyelids. However, that doesn’t mean they’re without protection. If you’re wondering what snakes have instead of eyelids, keep reading to find out!

What Are Eyelids Exactly?

When it comes to understanding a snake’s eyelids — or rather, lack thereof — it’s important to know what an eyelid is. After all, it’s more than just protection for your eyes.

Eyelids have a specific definition. They are folds of skin that are designed to sit over your eye with the ability to close as needed to provide protection and moisture. This means that they have their own muscles that connect to the brain and allow for movement.

Snakes lack both these muscles and these folds of skin. Instead, they’ve adapted a new way to keep their eyes safe. 

What Do Snakes Have Instead of Eyelids?

Instead of eyelids, snakes have what is known as a brille. You may also see this called other names, such as ocular scale, eye cap, or spectacle. A brille is a transparent layer that fits over the snake’s eye. The brille is attached to the snake’s eyes, however, so it doesn’t move around.

This also means that a snake’s eyes are always closed. If you were to close your eyes, you wouldn’t be able to see. However, because snakes have clear “eyelids,” they’re able to receive that same round-the-clock protection without sacrificing their eyesight.

If you’ve ever been near a snake, you may have noticed that their eyes always look glossy. This is because of the brille, which also helps keep their eyes moistened. Because the brille is transparent and doesn’t move, it’s usually hard to tell that snakes even have one.

Occasionally, when a brille is doing its job right, it may become scratched. While this doesn’t cause too much harm to the snake, it can obscure its vision. This is especially true since they are unable to move their brille, unlike eyelids. A snake’s brille does not heal itself in the traditional sense. Instead, it is replaced when the snake sheds its skin.

Do Snakes Blink?

Although snakes have their own form of specialized eyelids, they can’t blink. This is because their eye brilles are a covering over their entire eye. Blinking requires muscles to physically move the eyelids to close, which snakes lack.

Since snakes don’t have eyelids and can’t blink, they sleep with their eyes open. Usually, when you’re ready for bed, you need to close your eyes in order to fall asleep. For a snake, sleeping is as simple as their brain initiating the process. 

Why Snakes Don’t Need Eyelids

You’ll be surprised to learn that it isn’t actually a matter of snakes not needing eyelids, but rather that they need more.

You see, because snakes don’t have legs, they’re constantly on the ground. This means that their eyes are also being exposed to possible dangers such as dirt, dust, and debris. Eyelids are only fully protective when the eyes are closed. As a result, unless the snake slithered around with their eyes closed all day, they would still be at risk of eye injuries.

Because of this, snakes have evolved to have brille instead of eyelids as they provide constant protection. Since many other animals aren’t constantly exposed to dirt and dust like snakes, 24/7 eye protection isn’t as important for them.

Other Animals Without Eyelids

Eye brilles are actually fairly common in the world of reptiles. From snakes to certain lizards, to even some skinks, many reptiles don’t have eyelids. All of these species live their lives on or close to the dirt, and so eye brilles provide them with the best protection.

Many other species in the world don’t have eyelids, although they may not have brille either. Some bony fish, for example, have what is known as an adipose eyelid. This is a transparent “eyelid” that covers most of the eye, helping keep it safe without blinking. Frogs have eyelids and a nictitating membrane, which provides additional protection and moisture to their eyes.