The blind spot is the region of the visual field that corresponds to the location on the retina where the optic nerve leaves the eye. There are no photoreceptors at that point, so any light falling there produces no signal.

Each eye has its own blind spot, located about 15 degrees toward the temporal side of the visual field. Under ordinary conditions the gap is not noticed. The brain fills in the missing information from the surrounding pattern and from the corresponding region of the other eye. Simple demonstrations—closing one eye and moving a small mark until it disappears—make the blind spot obvious. The filled-in region can even take on the color or texture of the background, showing that the completion is an active constructive process.

The existence of the blind spot is a reminder that perception is not a passive recording of the retinal image. The visual system edits, interpolates, and stabilizes the input before it reaches awareness. Pathological scotomas—blind regions caused by disease or injury—are often noticed only when they become large or when they affect the central field, precisely because the same filling-in mechanisms remain active.

We do not see the hole in our vision because the brain has already patched it.