My eye doctor calls it a migraine
...Although it usually doesn't hurt like a migraine headache would.
Apparently, the curve widens until it can no longer be seen. This usually takes about 20 minutes.
Your eye doctor has books with pictures...but they don't sparkle and flash colors the way mine did.
I learned about mine when doctor was watching the pressure in my eyes which was a borderline signal for glaucoma, over several years. 'No change' is very good news, I learned.
I don't know how these 'migraines' figure into the equation, but, tidying up my diet, they have stopped.
I feel that if they start, something in your diet has caused it. Eliminating all commercially-prepared foods for a while should make a good difference. When, and if, you take some back, you may even be able to tell which ones are the culprits.
Good luck!
fledgling