The hole in your eye: How to find your optic blind spot

Watch reality vanish before your eyes

The hole in your eye: How to find your optic blind spot

The hole in your eye: How to find your optic blind spot 1920 1080 Looking out Loud

In brief:

  • A quick activity to learn a surprising fact about how your eyes see the world
  • A visual explanation to spark curiosity about biology (plus, why octopuses are different)
  • Ages: best for older kids (8 to adult) because it takes brief concentration

Did you know your eye has a blind spot? It’s true: there’s a little spot of the world directly in front of you that you can’t see right now.

Below I’ll explain what’s happening. First, watch reality disappear right in front of you.

How to “see” your optical blind spot

1. Hold this in front of you with your nose between the R and the L. If you’re looking on your phone, turn your screen horizontally to make the images bigger.

in post blind spot


2. Close your left eye

3. Stare at the R with your right eye. Don’t look around. Notice that you can still see the L on the right, but stay sharply focused on the R.

4. Very slowly move your face toward the screen (or your phone toward your face), keeping your right eye focused on the R. At some point, the L will disappear completely.

For me, the L disappears when my face is about 7 or 8 inches (15-20 centimeters) from the image. But it depends on your eyes and the size of your screen.

Tip: It can take a few tries to find the right distance. When you first notice the L looking blurry or fuzzy, stop moving the image toward you, and slowly adjust the distance between your eye and the image. Your open eye wants to move around, but force it to stay laser focused on the R.

Try it yourself. Then try it with your kids. My kids 10 and 12 got it faster than I expected.

Once you discover it the first time, it’s much easier to find it again.

How does the optic blind spot work?

In the back of your eyeball is your retina (the red optic disc in the image), which has photoreceptor cells to detect light. The collected light is then sent down your optic nerve (orange color in the image) into the visual cortex of your brain to interpret the images you see.

So what is the blind spot? For some reason, nature built the eyes of most vertebrates so that the optic nerve passes through the retina, leaving a blind spot in your retina that doesn’t detect light. (there’s a cool exception to this that I’ll mention below)

The optic nerve isn’t at the exact center of the back of our eye, it’s slightly off to one side. That’s why when you do this experiment, your right eye is looking at the R, which is positioned to the left of your nose.

When your peripheral vision in your right eye is aligned with the blind spot, that area of your vision “disappears” because your retina isn’t detecting any light from that spot of the world.


Why don’t we see a blind spot in our day-to-day life?

For one, we usually have both eyes open, and each eye sees the world from slightly different angles. So any missing light from one eye is filled in by the other eye.

Our eyes are also in constant motion, shifting from one object to the next. These eye shifts, called saccades, occur so quickly that the blind spot is quickly filled as our eyes scan the world.

Finally, most of what we “see” in the world comes from our brain’s expectations of what’s in front of us, rather the just the information our eyes take in. And since we don’t expect there to be holes in the world, our brain fill in the gaps for us. Thanks brain.

Blind spot bonus: and octopus can’t turn a blind eye

There’s one group of vertebrates who don’t have a blind spot: cephalopods, like octopuses, squids, and cuttlefish.

This is because for some reason, nature built their eyes a little different than other species. Notice how in its eye, the retina (illustrated in red) is in front of the nerve fibers (illustrated in orange). This way, the optic nerve doesn’t need to pass through the retina, and so there is no blind spot. Pretty cool, right?

→ Want to see another trick of your eyes? You can make moving dots disappear and change colors just by paying attention.