What causes the vision distortions with migraine headaches?

Brain changes: Visual illusions have been a topic for many decades. Oliver sacks has written a great deal about them, most recently in his book hallucination. Brain changes occur during migraine that cause the illusions. Lewis carroll had migraines that caused effects he described in his stories to alice. We now call them alice in wonderland effects in migraine. Exact cause is still uncertain.

Migraine and vision: The visual disturbances are inherent to certain migraine types due to the electrical changes and impulses that occur in the brain as part of the headache complex. You should see a doctor who specializes in headache (neurologist). The neurologist can perform a wide array of tests including blood-work, imaging tests, and perform a work-up to rule out the cause of the headaches.

Electrical discharge: The visual changes often occur as a central arc of shimmering colored light that gradually expands and then dissipates. This phenomenon suggests that a pulsating front of neural discharge marches through the brain.

Spreading depression: We believe that migraine proceeds from the back of brain forwards with a neuronal inhibition starting over the occipital lobe, and mediated by changes in the brain stem, especially locus ceruleus. The visual process is not retinal, but brain mediated, and the term is called "spreading depression of leao".