Occasionally, I have the following problem with my vision, simultaneously affecting both eyes. My vision becomes increasingly limited, appearing like tunnel vision as peripheral vision gradually and progressively decreases down to a circle of maybe 10 inches, but I never completely lose light. This can last for about 10-20 minutes, maybe more, during which time I don t have enough clear vision to read, even large print, but I can still walk and see gross figures. This has never happened while exercising, no particular time of day, no pain, no nausea. Today when it happened, I checked my BP and it was only a little above my normal baseline.