Also with bright patterns and other disturbances? I have always had occasional very bad migraines accompanied bysickness etc, since early childhood. In my mid-fifties this new phenomenon happened. it was painless while I lost my sight. I thought I'd got a detached retina, or that I'd had a stroke. it lasted for an hour. i was completely blind. Someone called an ambulance and I was taken into hospital. They thought I'd had a brain bleed, but an MRI scan was ok. They kept me in overnight, and the next day told me they thought it was an unusual kind of migraine. That was about 8 or 9 years ago.
Since then I've had those episodes from time to time, never quite as bad as the first time, but bad enough. Uusually with bright patterns, sometimes with blurred or wavy vision, often with a headache afterwards, but the episode is painless. They leave me disorientated, feeling nauseous and sometimes unbalanced, as if I have vertigo. That can last for a few days. If I can lie down when it comes on then it goes more quickly.
Other, ordinary migraines have diminished, and these optical migraines are less frequent. I have a medication called Propranolol modified release. Last summer I saw a neurologist and he said that probably this medication was indeed reducing the frequency. My health is pretty good the rest of the time. I'm in my late sixties.
In his book on mibgraines, Oliver Sacks describes his own similar experiences.