Test your blind spot


English: blind spot


A blind spot is the area in the eye that does not contain any meaning cells so that one cannot see at a certain point. This is where the optic nerve enters the eye.
The blind spot occurs naturally in both eyes and is compensated for in everyday life by the other eye. But there are tests with which the blind spot comes to light.

How to test your blind spot

The position and effects of the blind spot can easily be experienced by anyone 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 backwards or forwards (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 it is the other way round.

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 let it slowly 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 move with your right index finger at the same height from right to left towards the left index finger. Continue to fix your left index finger. At a certain point, the right fingertip should disappear.

If the test fails, there can be several reasons. 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 photoreceptor 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 appears 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 has a white area as well.

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.

You may also be interested in the following topics:

  • How does seeing work?
  • Rods and cones - the photoreceptor cells in the eye

Illustration: Horizontal section through the left eyeball, seen from below
  1. Cornea - Cornea
  2. Dermis - Sclera
  3. Iris - iris
  4. Radiant Bodies - Corpus ciliary
  5. Choroid - Choroid
  6. Retina - retina
  7. Anterior chamber of the eye -
    Camera anterior
  8. Chamber angle -
    Angulus irodocomealis
  9. Posterior chamber of the eye -
    Camera posterior
  10. Eye lens - Lens
  11. Vitreous - Corpus vitreum
  12. Yellow spot - Macula lutea
  13. Blind spot -
    Discus nervi optici
  14. Optic nerve (2nd cranial nerve) -
    Optic nerve
  15. Main line of sight - Axis opticus
  16. Axis of the eyeball - Axis bulbi
  17. Lateral rectus eye muscle -
    Lateral rectus muscle
  18. Inner rectus eye muscle -
    Medial rectus muscle

You can find an overview of all Dr-Gumpert images at: medical illustrations

Recommendations from the editorial team

  • Anatomy of the eye
  • Retina
  • Yellow spot
  • Optic nerve
  • Color blind