I sometimes see bright lights in my peripheral vision. What does it mean?

Flashing lights. Some flashing lights are caused by a retinal tear or hole. You should consider seeing a local ophthalmologist if the flashing continues, since not all flashes are benign. Retinal tears can lead to retinal detachments, which can cause blindness.
"Ocular " migraine. Migraine does not require a headache. How long do the lights last? Do you see them with your eyes closed? In both eyes?