Vision happens primarily in the brain.

Spiral patterns seem to fold in and out as this disc rotates. If we focus on a stationary object, it suddenly appears to move – in the opposite direction.

What happens if you observe the rotating disc with one eye, cover that eye, and then look at the stationary object with the other eye? Something surprising that confirms an important fact: vision occurs predominantly in the brain, not so much on the retina of the eye!