I have experienced this phenomenon 3 times, 2 in the last 2 days. It happens in one eye at a time. It starts out as a peripheral blind spot, then after 5 or so minutes turns into a "shimmery" or watery appearance before going away. The whole thing last about 10-20 minutes. It does not accompany headaches. It does not move across my line of vision. It does not happen to both eyes at the same time. One day it was the left, and the next day it was the right. I am in my early 40's/female. no known health issues.