Seeing your Blind Spot

Diagram showing how to find your blind spot.  A person's
head is seen from the top.  Their right eye is focused on
an x to the left in front of them.  To the right is a
circular blob which will disappear when the blind spot of
the right eye covers it. Each of your eyes has a blind spot that corresponds to where the optic nerve attaches to your eyeball. So why don't we see some kind of black or gray patch where the blind spot is? Because your brain "hides" the blind spot! This page describes how to fool your brain into revealing where your blind spot is.

Not only can you find your blind spot, you can play tricks with your brain as it tries to fool you!

Here's how to find your eye's blind spot. You can only do it one eye at a time, and you have to be very patient and methodical. But if you are, this can be fun!

You might be able to use the image below. Check to make sure that the distance between the X and the dot is between 5 and 7 inches. (Between 12 and 18 centimeters.) If it isn't, then you'll have to draw your own X and dot about 6 inches from each other on a blank, white sheet of paper. I assume that you can use the following picture, though.

The words 'look here with your right eye' with an arrow
pointing to an x on the left.  To the right is a circular

Scroll this page up or down so that the picture is in the middle of your screen. Then cover your LEFT eye, and with your RIGHT eye, look at the X on the LEFT. (So that you're looking past your nose a little bit.) Now very slowly move your head closer or away from the screen, until the dot on the right disappears. Remember, you have to be looking at the X, as you notice the dot disappear.

An x on the left and a circular blob on the right with a
grey line behind them.

Now, scroll this page up or down so that the picture with the line through the dot and X is in the center of your screen. Follow the same procedure that you did above. If it worked, you should have noticed that the dot disappeared, but the line still went through that area! Your brain connected the line through your blind spot for you!

This page is a mirror (with some small modifications) of Seeing your Blind Spot by David and Lillian Blume. Permission has been granted to present it on the web.

color bar Small icon for Theory of Molecular Machines: physics,
chemistry, biology, molecular biology, evolutionary theory,
genetic engineering, sequence logos, information theory,
electrical engineering, thermodynamics, statistical
mechanics, hypersphere packing, gumball machines, Maxwell's
Daemon, limits of computers

Schneider Lab

origin:    2006 Apr 25
updated: 2011 Aug 12

color bar

U.S. Department of Health and Human Services  |  National Institutes of Health  |  National Cancer Institute  |  | 
Policies  |  Viewing Files  |  Accessibility  |  FOIA