This isn’t necessarily what optical migraines are: It’s entirely possible to have just the optical component without the pain, and you don’t always get anything as interesting as auras or bizarre wheels-within-wheels Old-Testament-angels visual hallucinations.
I have optical migraines and mine begin as a field of random flashes in the center of my field of vision that gradually expands into a field of ‘black static’ (think old-fashioned analog TV static, but black instead of white) with the flashes on the periphery. This changes shape to bracket the center of my field of vision on one side or the other (usually the right side, I think), and grows outwards like a shock wave with constant width but increasing radius until it’s grown all the way out of my visual field. This is associated with, at most, extremely mild pain at some undefinable location in my head.