Well I did some research.
This lady asked
This one actually makes sense, and applies to what you're looking for.
This lady asked
And Doctor X (must be unknown doc?) said this in reply:"After rubbing my eyes, why do I visualize a glowing green/yellow 'eye'"
AND WOO HOO!!! Listen to what I found!!Seriously, when you apply pressure to an organ you can, in some respect,
transfer energy to the organ. This is what happens in a "precordial thump"-
-[Proper term.--Ed.]--when a person strikes the chest of a patient who is in
ventricular fibrillation [Malignant heart rhythm that causes death rapidly.-
-Ed.]. The energy transfered by the "thump" can, sometimes, clear the heart
of its malignant rhythm.
Returning to the eye, the pressure is sufficient to trigger your
photoreceptors. The receptors--and your brain--have not "idea" how to
interpret the signal as anything but a "real" object in the visual field.
How the eye lets you "see" and exactly how the images make it to your visual
corices--and how you can "interpret" vision--proves a very complex subject.
If you need more information, I can provide references of varying
complexity.
--Doctor X
This one actually makes sense, and applies to what you're looking for.
In one demonstration-an example of advanced eye-poking-Professor Wolfe asked the audience to "take a couple of fists and push straight back on your eyes. Notice the patterns that appear."
One person described seeing black and white checkers. Another expanded on that by noting that the squares of the checkerboard appeared to grow larger with distance from the center.
Professor Wolfe acknowledged that "we don't actually know what [that checkerboard] is, but it looks like you could be looking at your own visual cortex," or the part of the brain that handles vision.
Further, he continued, the growth of the checkerboard squares could correspond to the organization of the visual cortex. The small "squares" in the center represent cells that can make out fine details. These cells don't extend across the whole visual field because the human brain isn't big enough to process all of the information that would come in if they did. So with distance from the center, cells get progressively larger and less capable of making out details.
In a brief aside, Professor Wolfe noted that some people see the same sort of "checkerboard" effect during migraine headaches. Here, he said, "you're almost definitely seeing your visual cortex."