It starts off quite innocently. You know what it's like when you look at something bright and it burns itself into your retina so that whatever you look at for a few minutes afterwards you can still see the burned image? Well, that's how it begins. Just a little diamond in the corner of my eye. Then over the course of about 20 minutes it arcs and grows until it finally grows out of my eye (which is the way I think of it).
It's centred over my left eye but I can see it with both eyes so I suppose that must mean it's my brain that is flipping not my eyes.
The first time it happened, about 20 years ago, I was petrified imagining this was the beginning of the end; now it occurs about twice a year on average and I know what to expect and can deal with it. Both the doctor and the optician said it's the kind of visual disturbance that migraine sufferers undergo; fortunately, if I do get a headache with it, it isn't too severe.
But as I was saying, the patterns it makes inside my eye are very Art Deco-ish. And now my head is just beginning to think about aching. Better finish the cleaning before it settles in.