Blind spot (vision)
Blindpoint of human eye
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Through Brain
Although all vertebrates have this blind spot, cephalopod eyes, which are only superficially similar because they evolved independently, do not. In them, the optic nerve approaches the receptors from behind, so it does not create a break in the retina.
The first documented observation of the phenomenon was in the 1660s by Edme Mariotte in France. At the time it was generally thought that the point at which the optic nerve entered the eye should actually be the most sensitive portion of the retina; however, Mariotte's discovery disproved this theory.
The blind spot in humans is located about 12–15° temporally and 1.5° below the horizontal and is roughly 7.5° high and 5.5° wide. Though harder to detect, the blind spot extends over the entire retina as angioscotoma.
History
The blind spot was first discovered by the French scientist Edme Mariotte in the 17th century (around 1668). He was experimenting with vision and noticed that there was a point in the visual field where no image was perceived. This contradicted the earlier assumption that the entire retina was capable of detecting light. He presented this finding in the court of King Louis XIV of France and also to the Royal Society of London, sparking further interest among scientists and philosophers.
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Blind spot test
Night blind spot
It is estimated that once fully adapted to darkness, the rods are 10,000 times more sensitive to light than the cones, making them the primary receptors for night vision. Since the cones are concentrated near the fovea, the rods are also responsible for much of the peripheral vision. The concentration of cones in the fovea can make a night blind spot in the center of the field of vision for very dim objects.