I have recurring ocular migranes. what is causing this?

Migraine represents hereditary undue sensitivity of glutamate to inner and outer triggers. You likely possess "classical migraine", and the episodes can be prevented with appropriate interventions. See a neurologist.

There are several possible causes of ocular migraines. The most commonly overlooked cause is temporal muscle tension commonly caused by emotional tension or commonly a possible temporomandibular joint disorder. I would expect the muscle to be tender to pressure and to fatigue under excessive activity such as chewing gum or opening the mouth wide.