This happened to me again just now: http://en.wikipedia.org/wiki/Scintillating_scotoma. It starts as a blurry spot that obscures the center of the vision and then grows outward concentrically in a ring or crescent shape until it finally disappears after 20 minutes or so. It affects both sides of vision, as it is apparently something that happens in the brain, not the eyes.
I don’t like it at all. It keeps me from effectively using the computer, reading, driving, etc for up to a half hour. Fortunately it doesn’t cause any pain, only visual disturbance. Various articles I’ve read explain that it’s related to migraine. They say there’s no need to seek treatment unless you’re experiencing pain. Indeed, there is apparently no treatment for the visual effect.
It has been happening to me every few months for probably 10 years. The first time, I was working at Michaels and I thought I might have to go to the hospital. But it faded quickly, and I looked it up online afterward.
This is an excellent depiction of what it feels like (focus on the center of the image):
Bodies are so weird.
Have you ever experienced anything like this?