Scintillating Scotomas

Seven or eight years ago, I was in the office, working on a PC screen full of text as usual, when I realized I could not see correctly.
Wherever I looked, the central letter disappeared, as though I had been dazzled by a small bright light.
In both eyes.
I immediately thought of macular degeneration & panicked.

After a few minutes, the blind spot started migrating to one side, with central vision restored.
At that point I thought "stroke?" & went to the medical office where I was told to lie quietly in the dark.
After half an hour things seemed to be back to normal, so I gradually forgot about it.

A year or so later, the same thing happened again.

Since then I have had another 37 "attacks" & now recognize all the symptoms.
It always starts with loss of central vision in a small area, like one letter of text.
It is always EXACTLY the same in both eyes, a good clue to it not being an eye problem at all.
The blind spot always moves off-center, becoming an irregular 'C' shape if moving left, or reversed 'C' if moving right.
It can go more or less left or right, but never straight up or down – usually between 1 & 5 o'clock or 7 & 11 o'clock.
As it moves away from center, it increases in size & thickness.
It keeps moving in roughly the same radial direction & keeps roughly a 'C' shape.
As it increases on size & area, the blind spot fills with bright scintillating blue, brown & gold zig-zags, as though I had looked too close at the filament of a light bulb.
I can see the scintillation even with eyes closed, just like when dazzled.
It takes 30-35 minutes to disappear from the field of view.
For 10-15 minutes afterwards, I am aware of "something" undefinable – if I say visual numbness, that is as near as I can get.

Now I am used to it, I no longer need to stop any activity – I just need to deliberately "scan" if reading etc.

I have kept records, after the first couple of events, to try to correlate to time, activity, stress, mood, food & drink, temperature and so on, but I don't find any link at all.
Frequency is gradually increasing, which is a pity, but I can have events a couple of days apart & then not for 6 months.
Doctors didn't find any cause or offer any explanation.

Eventually, by Googling, I started to home in on "Scintillating Scotoma" which turns out to be quite common, though hardly anybody knows the term, and which matches my symptoms perfectly.
Apparently it is a type of migraine, though in many cases completely without pain.
The exact mechanism seems to be unclear.
Different people report varying degrees of relief with dietary changes, but my interpretation is that the results don't look significant.

Several hundred sufferers have found Edith Frost's website dedicated to this subject & have described their experiences – generally relief at finding they are not alone, crazy, or, apparently, seriously ill.
Nobody seems to suggest the condition degenerates to anything very worrying.
The site has now shifted to Google Groups at http://groups.google.com/group/scintillating-scotoma

Parting thot: "The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka!" but "That's funny..." - Isaac Asimov