The retina is the nervous tissue that covers the part of back of the eye. On her the images form that give the vision sensation us. Llmadas is formed by some especially sensible cells to the light cones and rods. The retina is connected to the brain by means of the optical nerve. The point in which this one is united to the retina denominates blind point to lack photosensitive cells (sensible to the light).

Normally we did not perceive the blind point since when seeing an object with both eyes the part from which arrives on the blind point of one from them, affects a sensible zone of the other. If we closed an eye either we will not be conscious of the existence of the blind point because the brain normally deceives and completes the part to us that lacks of the image. This is the reason that the existence of the blind point was not well-known until century XVII.

An experiment to verify the existence of the blind point

  • In a fine cardboard it draws a cross and a circle as it is seen in the following figure:

  • It places the fine cardboard to about 20 centimeters of the right eye.

  • It closes the left one, it looks at the cross with the right eye and approaches the fine cardboard slowly.

  • It will arrive a little while in which the circle will disappear of the field of vision. At this moment its image forms on the blind point.
  • When continuing approaching the fine cardboard, the circle returns to appear.