If you close your eyes and gently, at first, apply pressure to your eyeball at the corner nearest to your ear, you may see an aura.
No? Well try a little more pressure, but not enough to cause discomfort. Let alone, sudden loss of your aqueous humor.
If you are not aura-impaired, you saw an oval foamy white cloud in the visual field opposite to where you stuck your finger (toward your nose). Some report sensations of color in the oval, with smearing outside the oval.
It is not reccommended that you try this experiment often. Or with pointed sticks.
As for the migraine vision, I had it 3 times. I had seen the figure drawn by a doctor 100+ years ago, and published in a medical journal, showing the bright zig-zag spiral people sometimes experience before a migraine.
So I was lecturing some years later and I started getting one - the visual stuff, not a migraine. So I drew it on the board, asked, "Anyone know what this is?"
"Oh man, you gotta migraine."
Similar responses from about 1/10th of the class.
Is that quality qualia, or what.
