Blind spot of mariotte -

A blind spot, scotoma, is an obscuration of the visual field. A paicular blind spot known as the physiological blind spot, "blind point", or punctum caecum in medical literature, is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through the optic disc. Because there are no cells to detect light on the optic disc, the corresponding pa of the field of vision is invisible. Some process in our brains interpolates the blind spot based on surrounding detail and information from the other eye, so we do not normally perceive the blind spot. Although all veebrates have this blind spot, cephalopod eyes, which are only superficially similar, 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 poion of the retina; however, Mariotte's discovery disproved this theory.