Are short lasting sparks of light in your periphery a common sign of brain tumors? my eye doctor couldn't find anything wrong.

Best to see Ophtho: There are conditions that can cause your symptoms. One of them is cephalic migraine, but there are also conditions in the retina and the optic nerves that can do that. It is best to see an ophthalmologist and possibly one who is also good at migraines to make the differentiations and hopefully your peace of mind. I don't know if you saw one or an optometrist.