I’ve had them, jagged colourful patterns in my eyes but no other symptoms. No pain, no dizziness, no nausea, but can last for a good two hours. The cure for me is just to go and sit or lie in half-darkness and wait.
The trigger is a flash of sunlight, usually reflected off a window as it is opened or closed.
The first time I remember this happening was at work in about 2002 when I was in an office looking out over a courtyard to another office building. The way the building was cabled with everything running round the outside walls meant our desks were around the walls, facing outwards, so when I was looking at my terminal screen, I was also facing that other building. And one day, with the sun full on it, somebody opened a window and FLASH! Triggered.
My mum used to get migraines, though hers were triggered by bananas (just the smell would set her off), and hers used to be very painful and last for up to four hours.