This particular swirly effect is a real visual phenomenon. He wasn't just being avant garde. He was painting exactly what he saw.
It originates from the nerves that control your eyebrow. There are two of them on each side.
How I know:
My supraorbital on the left side gets inflamed. If I wear a hat, this will happen.
But only on the left side of my left eye. The rest of my vision is normal. So trippy when it happens...
It's way different than my other hallucinations which emanate from the bottom of the field and manifest when my eyes are closed. This really is like looking through water running down over the eye. I thought it was a stroke at first, but it stops if I remove the hat.
