A related discussion,
Visual disturbance was started.
When I stand up for long periods of time or when I receive some kind of physical shock the same kind of thing happens to be except that my patches are black and eventually I can't see anything at all. It could be caused by Neurally Mediated Hypotension which is just when your brain miscommunicates with your heart and drops your blood pressure when you actually need it to rise. It is common in young adults. Drinking Sundrop and eating more salt can help and if it happens just lie down and it should go away.
I can only guess at this but it sounds similar to what I have had over the years except a little different. I call them 'spells' now as I know what's coming. Mine are from the onset of a migraine. My mother has the same spells except she doesn't get the migraine after like I do. It's very strange. You should see your Doc though. It could even be your Thyroid or BP. *hugs*
I have fibromyalgia, but about five or six years ago I would have bouts of that. It would get worse when I was outside in the heat. I went to the doctor and he thought they could have been "physical anxiety attacks". Have you been under a lot of pressure lately?