What are eye flashes? what do you see when it happens? do you feel pain or anything during that? is it a constant symptom for a while once happened?

Many types: of flashes can occur in the vision. Classic migraines cause moving lines of brightness that impairs the peripheral vision and occur in both eyes simultaneously. A pull on the retina from a vitreous detachment causes a flash like lightning in just one eye. Other retinal diseases can cause flashes as well. There can pain with some types and not with others. Flashes are serious symptoms.