What Causes Flashes Of Light In The Field Of Vision?

Good afternoon Doctor: I am a 69 year old Caucasian mail. I was diagnosed about ten years ago with implacable trigeminal neuralgia with break-out pain. I take carbomezapine, Neurontin, and baclopen. Although I have had a couple of major attacks requiring hospitalization, my pain is presently under control. My question is this: yesterday I began to have a problem with my vision. If you ve ever taken a photograph with a camera, you may have observed that your vision shutters while the picture is taken. I.e., you lose sight for a split second, and then your vision returns. That s what been happening to me since yesterday morning; for brief, sporadic episodes. I have no history of heart attack or stroke.