Ocular migraines! Ocular migraines are a form of migraines that take place in the occipital cortex (part of the brain that interprets/controls vision). They lack the severe headache as common migraines. The symptoms are usually all or mostly visual and are typically described as flashing of light or ziz-zag lights in the vision. They usually last less than 30 minutes and affect the vision out of both eyes.
Great question . We dont know. There are genetic and environmental factor that make them more likely but we don't full understand the cause.
Chronic head tilt. Cause is a chronically tilted head, causing superior trapezium leading edge girth inequality; thinnest trapezius on head-tilt side!, and other side (head support side) develops spasm, isometric strengthening, greater leading edge girth, and pain generating trigger points.