Does dehydration cause ocular migraine?

Possibly: It can certainly be one of many precipitating factors. If that is what you've noticed causes your migraines, then that is a relatively easy thing to prevent. However you should get checked by your doctor.

Ocular migraines!: 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. Dehydration in possible, as well as stress, or something in your diet - Caffeine, chocolate, etc.