The eye is formed during embryonic development by a combination
of head ectoderm and neural tube tissue, the latter forming the
retina. Thus, the retina is not a peripheral sensory organ like
skin touch receptors or taste buds on the tongue, but rather it is
an outgrowth of central nervous tisse. Because of this origin, the
retina has layers of neurons, internal circuits, and transmitters
characteristic of the brain: it is a bit of the brain that has
journeyed out, literally, to have a look at the environment.
Copied from a website.
Since the eye is a bit like the brain, I think the jumping of
neurons causes the worm-like thingy.
