3D image of my right eye optic nerve. 2017 ©
When this image is viewed by adjusting the focal points of each eye so that they are each looking at the left or right hand side of the image respectively (i.e. diverged and parallel with each other) a central third image will appear in 3D. Or, when you see 4 optic nerves, try to make the centre two overlap each other. It is the same viewing principal as a ‘Magic Eye’ picture.