We have a blind spot in our vision because the optic nerve, which carries visual information from the eye to the brain, must exit the eye through a spot on the retina that has no light-detecting photoreceptor cells. This creates a gap in the visual field where no image is detected, known as the blind spot or physiological blind spot. The brain compensates for this gap by filling in the missing information based on surrounding details and the input from the other eye, so we typically do not notice the blind spot in daily life.
This blind spot arises as a result of the structure of the human eye, sometimes referred to as an "inverted eye" design, where the optic nerve fibers pass through the retina to exit the eye, causing this unavoidable hole in the retina. Some other animals, like cephalopods (squids and octopuses), have differently structured eyes that lack this blind spot because their optic nerves do not pass through their retina in the same way.
