A blind spot, scotoma, is an obscuration of the visual field. A particular blind spot known as the blind spot, 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. Since there are no cells to detect light on the optic disc, a part of the field of vision is not perceived. The brain interpolates the blind spot based on surrounding detail and information from the other eye, so the blind spot is not normally perceived.
Although all vertebrates 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.