Visual illusion
The Blind Spot
Discover the physiological hole in your vision where the optic nerve exits the eye, and see how your brain 'fills in' missing data.
The Illusion
Every human eye has a blind spot (scotoma) roughly 15 degrees from the center of vision. This is the point where the optic nerve fibers pass through the retina to exit the eye and connect to the brain. At this specific location, there are no photoreceptor cells (rods or cones) to detect light.
Why Don’t We Notice It?
We rarely notice this gap in our vision for two reasons:
- Binocular Vision: The blind spots in our left and right eyes do not overlap. The left eye sees what the right eye misses, and vice versa.
- Perceptual Filling-in: Even with one eye closed, we don’t see a black hole. The brain actively interpolates (“fills in”) the missing area based on the surrounding visual information (texture, color, or lines).
The Demo
This tool demonstrates both the existence of the blind spot and the brain’s filling-in mechanism.
- Disappearing Dot: Standard proof. The dot vanishes when it hits the blind spot.
- Magic Line Repair: A broken blue line has a gap. When the gap hits the blind spot, the brain connects the two blue segments, making the line appear continuous.
- Yellow Filling: A blue dot on a yellow background turns yellow when it disappears, proving the brain fills with the background color.