It is the only area of the retina which does not see, because of the lack of photoreceptors. It corresponds to the place where the optic nerve and the blood vessels leave the eye.( image below )
It is a spot in the visual field where objects are not seen.
It is at the XVIIth century, while proceeding to the dissection of a human eye, that the French physicist Edme Mariotte discovered the blind spot, area of the retina where the optic nerve is attached to the ocular sphere. It suspects that being deprived of photoreceptors cells, the light does not stimulate this area and that, consequently, each eye have a "blind spot", a small area of the visual field where it is blind. It shows it with the illustration which follows.