Kathy, I get these visual migraines on occasion. For me they are unrelated to the VM. Mine are triggered by certain light conditions, namely bright grey natural light. Twice they have occurred when I have been washing up and the light has shone on the silver cutlery and dazzled my eyes somehow. I get approx one per year for the last 10 years.
Dr Surenthiran advised me that different parts of the brain are reacting with different types of migraine. So with normal headache migraine it is the blood vessels around the brain that are in play, the visual migraines come from the optic part of the brain and the vestibular migraines are from the brainstem area which controls balance.
So there is a chance the scotoma is not related to the VM or the medication you are taking x