I'm seeing bright zig zag lines in my left eye that last about 20 minutes. what could be the cause of this ?

Migraine?: I suspect a migraine aura which you could see at night or any other time. If you've never experienced this symptom before, make an appointment to see an eye md to reassure your eyes are okay. If you have other symptoms such as headache, nausea, & vomiting, medications may be prescribed if particularly frequent and severe. Usually tees events are stress related. May also have other triggers(food)