Also known as scotoma, a blind spot is a specific section in the eye/retina which does not have receptors that react to light. In lay man’s terms, a blind spot can be referred to as a tiny section in the eye without vision. Every human has a physiological or natural blind spot in the vision. The blind spot was first observed and documented in mid-1600 in France by Edme Mariotte. During this period, doctors were of the opinion that the entry point of the optic nerve into the human eye was the retina’s most sensitive section. Edme’s discovery disproved this belief.

The blind spot is situated inside the eye at the upper end of the optic nerve. This nerve carries several nerve fibers from the brain to the eyeball. It enters into the eye through the back and scatters nerve fibers across the back, thus creating the retina in the process. The retina is a layer composed of light-detecting cells. The tiny circular entry spot of the optic nerve located at the back of the eye is known as the optic disc or optic nerve head. It does not have any light-detecting cells. Thus, each eye has a visual field with a small ‘blind’ gap.

The blind spot is situated 1.5 degrees under the horizontal and around 12 to 15 degrees temporal. Its width is approximately 5.5 degrees while the height is 7.5 degrees. Most species of vertebrates have a blind spot in vision. However, in cephalopod eyes, which are somewhat identical to the human eye, the optic nerve accesses the receptors from the rear. Subsequently, no break is created in the retina, thereby preventing the development of a blind spot. The visual field of each eye overlaps each other so as to overcome the effects of the blind spot. The brain efficiently uses different kinds of spatial data and information from the second eye to fill up any missing visual data. The process of guessing the missing information is continuously carried out by the brain. Because of all these reasons, we typically do not notice our blind spots.