Anatomy-Lexicon

Test your blind spot

Synonyms

English: blind spot

introduction

A blind spot is the area in the eye that does not contain any sensory cells that can receive light so that a certain point cannot be seen. The forming spot occurs naturally in both eyes.

How to test your blind spot

Anyone can easily experience the position and effects of the blind spot with a test.

After closing or holding the left eye, focus on the X with the right eye.
Now change the distance to the screen by moving your head forwards or backwards (while still focusing on the X) until the O is gone.

The same thing works with the left eye, of course, while closing the right eye and concentrating on the O.

More ways to test

Testing the blind spot is amazingly easy. All you need is a piece of paper and a pen. Draw a small symbol, such as a cross or a letter, on the sheet. About 10 to 15 centimeters next to it, draw a second symbol at the same height. Using two different symbols can simplify the assignment.
Alternatively, you can also use ready-made test cards. These can be found on the Internet, for example.

As long as both eyes are open, the brain is able to compensate for the blind spot, so you have to close one eye. In the right eye, the blind spot is on the right-hand side in the field of vision; in the left eye, the opposite is true.

If you want to test the blind spot of your right eye, close your left eye and fix the symbol drawn on the left. Now change the distance between the paper and your right eye.
It is best to hold the sheet of paper in front of you at about eye level with your outstretched arm and then slowly let it wander towards your face. Keep the left symbol fixed and exactly in the middle of your field of vision. At a certain distance, the symbol on the right should suddenly disappear. It is now right in the blind spot.

To test the blind spot of your left eye, simply repeat the test, but this time fix the right symbol and close the right eye.

Alternatively, you can hold your left index finger in front of you and fix it. To do this, close the left eye again. Now wander with your right index finger from right to left at the same height towards the left index finger. Keep fixing your left index finger. At a certain point, the right fingertip should disappear.

If the test fails, there can be several causes. Both symbols should be exactly at the same height next to each other. Hold the sheet at about eye level. Make sure that you have completely closed the eye that is not in use and that you have fixed the correct symbol. Do not take your eyes off the correct symbol while testing.

Accordingly, you should only perceive the second symbol in the field of vision. A little experimentation with the correct spacing may be required, especially at the beginning. Once you have some feeling for the correct distance, the test becomes very easy.

Explanation of the blind spot

There are no visual cells at the blind spot, so the brain actually lacks any image information at this point. You may have noticed that the blind spot is still not perceived as completely empty or black. Rather, the brain uses the information from the surrounding visual cells to compensate for the missing image information.
The blind spot is basically the place where the optic nerve bundles on the retina.

If you use a sheet of white paper, the place where the symbol was previously appears appear white. The brain estimates the missing image in the blind spot from the environment. The surrounding sheet is white, so it's only likely that the missing spot is also white.

This simple test impressively shows a few basic properties of our vision. What we perceive as an exact picture of our surroundings is actually information that has already been processed and prepared by the brain. The brain lacks visual information at the blind spot. However, it is able to skillfully compensate for this deficiency so that it is never noticed in everyday life.