Each of your eyes has a blind spot, but your brain fills in the gap so you never notice it.

Where the optic nerve exits the back of each eye, there are no light-sensitive cells, which creates a small gap in your visual field called the blind spot. It sits off to the side of your central vision in each eye, and under normal two-eyed viewing you never notice it, because each eye covers the other’s gap, and your brain actively fills in the missing patch using surrounding visual information and context.

You can actually find your own blind spot with a simple test: close one eye, focus on a fixed point, and move a second small object off to the side at the right distance until it seems to vanish. The fact that a literal hole in your visual data goes completely unnoticed in everyday life is a vivid demonstration of how much of what you “see” is actually constructed by the brain rather than directly recorded from the world.