Hi.
I finished a 30 day course of cipro and I had the exact same symptoms with the black spot disappearing. My eyes are under treatment at the VA/UAB clinic in Birmingham, so I went there immediately after this happened. They injected a dye in my arm and took pictures of the retina. They diagnosed this as a hemorrage of a number of blood vessels. They had no idea of the cause and said it should heal. I go back October 3 for another check. Until then I have to make sure I don't lift anything heavy or do anything else to prevent strain on the eye. (I'm blind in one eye and this is appearing in my only good one.)