Starts with a faint flickering, like a ceiling fan off to the left, somewhere in the periphery.
Then comes the flashing, much as you portrayed it, the blind spots and the aphasia. More recently my cognitive skills have been diminished somewhat. I've only had the pain a couple of times but the agony is forever etched in my mind.
It's over in about 20 minutes to half an hour but I stumble over words for the next couple of days.
Usually brought on by glancing at a light. A Bic lighter is enough but halogen lights and the sun on rear windshields are killers.
Things to avoid... cheese and chocolate.
Bugger!