What If? Lab
What if you never blinked?
Blink! You do it all day without even thinking. Each blink spreads tears that keep your eyes wet and clean. What if you never blinked? Let's find out with Olly!
You blink about 15 times a minute, mostly without noticing. Each blink spreads a thin layer of tears across your eyes to keep them moist and wash away dust. Imagine never blinking again, then discover what tears do, why eyes feel dry, and how fish and snakes manage with no eyelids that close.
Blinking spreads tears from the lacrimal glands over the surface of the eye, keeping it moist and washing away particles; the American Academy of Ophthalmology gives a normal rate of about 15 blinks a minute. This thought experiment removes blinking and compares animals whose eyes are kept moist in other ways: fish in water, and snakes behind clear, fixed scales.
The big question
Blink! Your eyelids close and open very fast.
You blink all day long without thinking about it. What if you never blinked at all?
Try not to blink for a little while. It gets harder and harder, doesn't it? Your eyes want to blink, and before long they do.
Blinking happens so often that we hardly notice it. But it's doing an important job. So what if you never blinked? What would happen to your eyes, and how do animals that can't close their eyes manage? Let's follow the clues: tears, dry eyes, and fish and snakes.
Blinking is so frequent that it is mostly automatic, though it can also be done on purpose. The American Academy of Ophthalmology (AAO) describes it as the eye's way of getting the moisture it needs on its surface.
This thought experiment removes blinking while keeping tear production. It follows three threads: what tears do, what happens when the eye's surface is not kept moist, and how animals without movable eyelids, such as fish and snakes, keep their eyes protected.
Explore the idea
Make a prediction
What does a blink do for your eyes?
What is the main job of blinking?
What does each blink chiefly do for the eye's surface?
- Spreads tears to keep the eye wet
- Makes your eyes see colors
- Helps you hear better
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Established fact
Blinking spreads tears to keep your eyes wet.
Blinking is the eye's way of getting the moisture it needs on its surface; people blink about 15 times a minute.
Blinking supplies moisture to the eye's surface; the normal rate is about 15 a minute, falling to 5 to 7 at screens (AAO).
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Established fact
Tears wash dust out of your eyes.
Tears from a gland above each eye flow across it and wash away tiny particles.
Lacrimal tears wash foreign particles from the eye's surface and drain to the nasal cavity (OpenStax).
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Established fact
Fish and snakes never blink.
Most fish don't need eyelids underwater, and snakes have clear, fixed scales over their eyes instead of eyelids that close.
Most fish lack eyelids because water keeps the eye moist; snakes' fused spectacles protect the eye and prevent drying (Cousteau Society; PBS NOVA).
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An idea scientists discuss
If you never blinked, your eyes might feel dry and scratchy.
Without blinking, your eyes might often feel dry, scratchy or stingy, a bit like after a long time at a screen.
Absent blinking, the ocular surface would likely dry; the severity cannot be predicted here.
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Established fact
People blink about 15 times every minute.
People normally blink about 15 times a minute, and blinking is how the eye gets the moisture it needs.
Humans normally blink about 15 times a minute; blinking is the eye's way of getting moisture on its surface (AAO).
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An idea scientists discuss
Without blinking, your eyes might feel dry.
Without blinking, your eyes might dry out and feel scratchy, even though you still made tears.
Without blinking, tear production would continue but the surface film would not be renewed, likely causing dryness.
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Established fact
Tears wash dust out of your eyes.
Tears flow over the surface of the eye and wash away tiny particles; extra tears drain into your nose.
Tears from the lacrimal gland wash foreign particles from the eye's surface; excess tears flow into the nasal cavity (OpenStax).
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Established fact
Eyelids and eyelashes help keep bits out of your eyes.
Eyelids and lashes help protect your eyes by blocking bits that might land on them.
The eyelids, with lashes at their edges, help protect the eye from abrasion by blocking particles (OpenStax).
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An idea scientists discuss
Without blinking, dust might stay on your eyes longer.
Without blinking, tears might not sweep dust away as well, so bits could stay on the eye longer.
Without blink-driven redistribution, clearance of particles from the ocular surface might be slower; this is reasoned, not measured.
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Established fact
People blink less when they look at screens.
Studies show people blink only about 5 to 7 times a minute while using computers and other screens.
Blink rate falls to about 5 to 7 a minute during screen use, from about 15 normally (AAO).
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Established fact
Dry eyes can feel scratchy.
Dry eye happens when eyes don't make enough tears to stay wet or the tears don't work well; it can feel scratchy or stinging.
Dry eye occurs when tears are insufficient or ineffective; symptoms include a scratchy feeling, stinging or burning, redness and light sensitivity (NEI).
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An idea scientists discuss
Without blinking, people might need to keep their eyes wet some other way.
A person who never blinked might need another way to keep their eyes moist, a bit like how animals that can't blink have their own tricks.
A non-blinking human would likely need an alternative means of keeping the ocular surface moist; which one is speculative.
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Established fact
Fish don't need eyelids, because water keeps their eyes wet.
Most fish don't have eyelids: living in water, their eyes don't dry out.
Most fishes lack eyelids because, living in water, their eyes are in no danger of drying out; some, such as sharks, do have them (Cousteau Society).
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Established fact
A snake's eyes are covered by clear scales, so snakes never blink.
Snakes' eyes never blink or close: each is covered by a clear, fixed scale called a spectacle, formed from fused eyelids.
Snake eyes are covered by clear, immovable spectacles; evolution fused the eyelids to protect the eyes and prevent drying (PBS NOVA, 2013).
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An idea scientists discuss
If people never blinked, maybe we would need clear covers on our eyes like snakes!
A never-blinking person might need something like a snake's clear spectacle to keep their eyes from drying out.
A fixed, transparent cover like the snake spectacle is one evolutionary answer to the problem blinking solves; whether it could work for humans is speculation.
Blinking in our world
You blink about 15 times every minute.
Each blink is like a tiny windshield wiper. It spreads tears over your eyes to keep them wet.
The American Academy of Ophthalmology says people normally blink about 15 times a minute. That's about 900 blinks an hour!
Each blink spreads tears across the front of your eye. Tears are made by a gland just above and to the outside of each eye. They flow over the eye, wash away dust and tiny bits, and drain away in the inner corner of the eye. Your eyelids and lashes also help block bits that might land on your eyes.
The AAO gives a normal rate of about 15 blinks a minute, falling to about 5 to 7 a minute while people use computers and other screens. Each blink renews the moist film on the eye's surface.
OpenStax describes the plumbing: tears are produced by the lacrimal gland, located just inside the orbit, above and to the side of the eyeball. They flow over the surface of the eyeball and conjunctiva to the inner corner of the eye, washing away foreign particles, and excess tears drain into the nasal cavity. The eyelids and lashes help protect the eye from abrasion by blocking particles.
Switch blinking off
Now pretend you can't blink. Your tears are still there.
But nothing spreads them over your eyes. Your eyes might feel dry and scratchy.
If you never blinked, your eyes would still make tears, but nothing would spread them evenly across the front of your eyes. The surface might start to dry out between the tears.
We get a small taste of this when we stare at screens: the AAO says we blink only about 5 to 7 times a minute then. The National Eye Institute says dry eyes can feel scratchy, sting or burn, and look red. Without any blinking, your eyes might feel like that much of the time. That last part is an idea about a pretend body.
Without blinking, tear production would continue but the film would not be redistributed, so the surface would likely dry unevenly between drainage and evaporation. The National Eye Institute (NEI) explains that dry eye happens when the eyes don't make enough tears to stay wet or the tears don't work correctly, and lists a scratchy feeling, stinging or burning, red eyes and light sensitivity among its symptoms.
The screen effect offers a mild real-world parallel: blinking falls to about 5 to 7 times a minute, and NEI notes dry eye can happen if you spend a lot of time looking at a computer, tablet or phone. A body that never blinked might face this constantly; how severe it would be is speculative.
Why eyes need to stay wet
The front of your eye needs to stay wet, like a fish in water.
Tears keep it wet and wash away dust. Blinking spreads the tears around.
The eye works best with a wet surface. A Naked Scientists answer from the University of Plymouth's Mark Briffa explains that the eye first evolved in the ancestors of fish, where water kept its surface moist all the time. In air, an eye could dry out.
So animals that live in air need ways to keep their eyes wet. For us, the answer is tears plus blinking: glands make the tears, and each blink spreads them like a wiper spreading water across a windshield.
Marine ecologist Mark Briffa of the University of Plymouth, answering for The Naked Scientists, notes that the vertebrate eye, the same basic structure in fish and humans, first evolved in the ancestors of fish; it suits an aquatic environment where its surface stays moist, and is less suited to air, where it could dry out.
Land animals therefore need a system to keep the eye's surface wet and clean. In humans that is a combination: NEI notes that glands above the eyes make the tears that keep the eyes wet, and the AAO describes blinking as how the eye gets the moisture it needs on its surface.
Eyes that never blink
Fish don't blink. Water keeps their eyes wet all the time!
Snakes don't blink either. A clear scale covers each eye, like a window.
Some animals never blink. Most fish have no eyelids, and they don't need them: underwater, their eyes are always wet. They can even sleep with their eyes open.
Snakes can't blink either. PBS NOVA explains that each snake eye is covered by a clear scale called a spectacle. Through evolution, snakes' eyelids fused into this fixed, see-through cover, which protects their eyes and stops them drying out. So the spectacle does the job our blinking does.
Briffa explains that fish don't have eyelids because, underwater, they don't need them; lacking lids doesn't stop them sleeping, and zebrafish have been observed sinking toward the bottom of the tank, tails drooping, as they sleep.
Snakes solved the problem differently. PBS NOVA reports that their eyes never blink or close because they are covered in clear, immovable scales called spectacles: evolution has fused snakes' eyelids to protect their eyes and prevent them from drying out. University of Waterloo researcher Kevin van Doorn also found that the spectacle carries blood vessels whose blood flow changes from moment to moment.
Amazing facts
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Some of your tears go into your nose!
Extra tears drain from the inner corner of your eye into your nose.
Excess tears eventually flow into the nasal cavity (OpenStax).
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Fish can sleep with their eyes open.
Fish have no eyelids, but they still sleep. Sleeping zebrafish sink toward the bottom of the tank, and their tails droop.
Lacking eyelids doesn't prevent sleep: sleeping zebrafish sink toward the tank bottom with drooping tails (Mark Briffa, The Naked Scientists).
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Looking at screens doesn't harm your eyes forever.
Eye doctors say looking at screens for a long time doesn't permanently damage your eyes, though it can make them feel tired and dry.
The AAO states that long periods at digital screens will not permanently damage the eyes, though reduced blinking can leave them strained and dry.
Words to know
- blink
- to close and open your eyelids quickly
- tears
- the salty liquid that keeps your eyes wet and clean
- eyelid
- the fold of skin that closes over the eye
- lacrimal gland
- the small gland above each eye that makes tears
- spectacle
- the clear, fixed scale that covers a snake's eye
- dry eye
- when eyes don't stay wet enough and feel scratchy or stingy
Discovery challenge
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About how many times a minute do you blink?
About how many times a minute do people normally blink?
What is a typical human blink rate?
- About 15
- About 1
- About 500
Show the answer
About 15
About 15 times a minute!
About 15 times a minute, but only 5 to 7 at screens.
About 15 a minute (AAO).
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Why don't fish need to blink?
Why don't fish need eyelids?
Why have fish no need of eyelids?
- Water keeps their eyes wet
- They have no eyes
- They sleep all day
Show the answer
Water keeps their eyes wet
The water keeps their eyes wet.
Underwater, their eyes stay moist all the time.
The aquatic environment keeps the eye's surface moist.
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What covers a snake's eye?
What covers a snake's eye instead of an eyelid that blinks?
What structure replaces blinking eyelids in snakes?
- A clear scale called a spectacle
- Long eyelashes
- A layer of fur
Show the answer
A clear scale called a spectacle
A clear scale, like a window.
A clear, fixed scale called a spectacle.
The spectacle: fused, transparent eyelids (PBS NOVA).
Experiments to try
- Watch What If? Lab What if you had no sense of balance? Deep inside each ear are tiny loops filled with fluid. They tell your brain when your head turns and tilts, and together with your eyes and the touch sensors in your legs, they keep you steady. Imagine losing that sense, then discover why spinning makes you dizzy and how astronauts relearn their balance back on Earth.
- Watch What If? Lab What if you could see like an eagle? Some eagles can see about twice as much fine detail as people can. Their big eyes are packed with light-sensing cells, and many birds of prey have two extra-sharp spots in each eye where we have one. Imagine trading eyes with an eagle and find out what you would gain, and what eagles might not see at all.
- Watch What If? Lab What if you never got hiccups? A hiccup is a sudden twitch of your diaphragm, the dome-shaped muscle under your lungs that helps you breathe. Then your vocal cords snap shut and make the 'hic' sound. Imagine never hiccuping again, and discover what scientists have found out about hiccups, from babies before they are born to the tricks people try.
Explore next
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Watch
3D
Animal
Goldfish
The goldfish is a small member of the carp family that people in China tamed centuries ago, by the time of the Song dynasty (960–1279). Wild goldfish are greenish-brown, but careful breeding has made gold, white, black and spotted pets with fancy fins.
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Watch
Animal
Corn snake
The corn snake is a slender, colorful snake of the pine woods, fields and old barns of the southeastern United States. It has red blotches outlined in black and a black-and-white checkered belly. It has no venom: it catches mice and rats by squeezing them, and it spends much of its time hidden in burrows.
- Watch What If? Lab What if you had no sense of balance? Deep inside each ear are tiny loops filled with fluid. They tell your brain when your head turns and tilts, and together with your eyes and the touch sensors in your legs, they keep you steady. Imagine losing that sense, then discover why spinning makes you dizzy and how astronauts relearn their balance back on Earth.
- Watch What If? Lab What if you could see like an eagle? Some eagles can see about twice as much fine detail as people can. Their big eyes are packed with light-sensing cells, and many birds of prey have two extra-sharp spots in each eye where we have one. Imagine trading eyes with an eagle and find out what you would gain, and what eagles might not see at all.
- Watch What If? Lab What if you never got hiccups? A hiccup is a sudden twitch of your diaphragm, the dome-shaped muscle under your lungs that helps you breathe. Then your vocal cords snap shut and make the 'hic' sound. Imagine never hiccuping again, and discover what scientists have found out about hiccups, from babies before they are born to the tricks people try.
- Watch What If? Lab What if everyone had the same fingerprints? The swirls and loops on your fingertips form before you are born, and no two people's are known to match, not even identical twins'. That's why fingerprints are used to tell people apart and to unlock phones. Imagine a world where everyone's fingerprints were exactly the same, and discover how they form, what they might be for, and what would change.
- Watch What If? Lab What if germs did not exist? We often think of germs as bad, but many of the tiny living things around us are harmless or even helpful. About as many microbes live in your body as you have body cells, and they help you digest food and help your immune system develop, and helpful bacteria turn milk into yogurt and cheese. Imagine a world with no microbes at all, and see what we would lose.
- Watch What If? Lab What if humans had tails? Many animals use their tails to balance, to signal to each other, or even to grab branches. People and apes have no tails, but we each have a small tailbone at the bottom of our spine. Imagine life with a tail, meet monkeys that hang by theirs, and discover what scientists learned in 2024 about how our ancestors lost their tails.
For parents & teachers
What children will learn
- Blinking spreads tears that keep the eye's surface moist and clean.
- Tears are made by a gland above each eye and drain into the nose.
- People blink less while using screens.
- Fish and snakes protect their eyes in other ways: water and clear spectacles.
Recommended ages: 4 to 17 · About 10 minutes
Talk about it
- Why do you think your eyes start to feel uncomfortable in a staring contest?
- How is a snake's spectacle like a pair of goggles?
- What could you do to remember to blink during screen time?
Try at home or in class
- Count how many times a family member blinks in one minute while chatting, then again while they watch a screen. Compare.
- Look at a goldfish or a fish picture and a snake picture. Where would eyelids be, and what does each animal have instead?
Key vocabulary: blink, tears, eyelid, lacrimal gland, spectacle, dry eye
Where these facts come from
- Computers, Digital Devices, and Eye Strain , American Academy of Ophthalmology
- Anatomy and Physiology 2e, §14.1 Sensory Perception , OpenStax
- Dry Eye , National Eye Institute (NIH)
- Why don't fish have eyelids? , The Cousteau Society
- Why don't fish have eyelids? (answer by Mark Briffa, University of Plymouth) , The Naked Scientists
- Frightened Snakes and Their Blood-Filled Spectacles , PBS NOVA
Checked, not yet human-reviewed. Last updated October 26, 2026. Spotted a mistake? Tell us.
Picture credits
- Photo: Kolforn (Kolforn) I'd appreciate if you could mail me (Kolforn@gmail.com) if you want to use this picture out of the Wikimedia project scope. This file is licensed under the Creative Commons Attributi, CC BY-SA 4.0, via Wikimedia Commons · source · license
- Photo: Peter Paplanus, CC BY 2.0, via Wikimedia Commons · source · license