Was very good to read so many people describing my symptoms and discussing their experiences in seeking medical and food-related answers.  I'm 48 and have experienced these half-hour spotty vision episodes that start in the middle of vision field and end in the pulsating peripheral lights, followed by dull headache for about 3 decades.  Often try to work through them but reading and focusing attention become nearly impossible for the middle 15 minutes or so.  Used to think it was hypo-glycemia and now believe it is definitely a nutritional imbalance or deficiency.  Have had periods over the last 30 years with a year or two without an episode and periods (like at present) where I'll get them nearly daily for several weeks to months.  Many, many times I have immediately gone to eat something to see if it helps.  Last 2 times was citrus and didn't help.  Next time will be an apple thanks to reading this blog.  Hope to someday learn exactly what this is and how to handle it.