The neural retina, lining the back of the eye, is a piece of the brain, making the brain very close to the external openings of the eyelids.

“at the back inner lining of your eyeball you have a very thin three cell layer thick piece of tissue that we call the neural retina and I say this because the neural retina is actually a piece of your brain so you have two pieces of brain that line the back of your eyes and that's the light sensing tissue in the back of your eyes now I say this because what this means is that it's a very short distance between the opening of your skin that we call your eyelids and your brain”