Those blind spells could be a warning sign called a TIA that comes before a major stroke. There's a test called "carotid ultrasound" which is non-invasive, (meaning it doesn't hurt, ) that shows if the arteries in your neck, going to your brain, are okay or if they have "plaque" in them. Plaque is the nasty stuff that can plug up blood vessels in either the heart or the brain-same process, same risk factors like high cholesterol.
The eye doctor can order this test. (I should know, I'm married to one.) A pre-stroke TIA is the most dangerous cause of the blind spells, with seizures running a close second. Insist that they keep working with you until both of those are ruled out.