I've got scintillating scotoma. what is causing it?

Migraine: Almost always this is due to occipital migraine (the occipital lobe is the portion of the brain which registers the vision). These migraines are usually benign, last several minutes to 2 hours, and are accompanied by greying out areas in one side of each eye surrounded by flashing lights (the scintillating scotomas). These fade with no trace and the eye goes back to normal.