Visual migraines can cause a shimmering, zig-zag light effect that lasts from a few minutes to 20-30 minutes. A headache sometimes can follow but often does not. You can use search engines to read about the diagosis and see if it might fit your symptoms. There are other possible ocular and neurologic causes so it is very important to discuss your symptoms with an ophthalmologist in your area and perhaps a neurologist. Regarding the eyes, I would want to rule out any iris defects, lens or lens zonule abnormalities, vitreous floaters, or retinal disease of some sort.
Michael Kutryb, MD