The picture, which has received thousands of shares, is a classic example of what is called a simulation, according to Jan Ygge, a professor of ophthalmology (eye diseases) at the Karolinska Institute.
- It's the same as when someone shoots with lightning and we feel that we have a black spot in the field of view. In the eye we have sight cells that react to different colors, red corresponds to green, blue corresponds to yellow and black corresponds to white.
In this case, the picture is negative.
- When we have stared at it long enough you can say that we burn out the cells, and when we look at the white surface we get the positive image, he says.
Hear Jan Ygge tell us more in the clip - and test yourself to look at the picture.