Hi, I am 57 y.o. Woman And work out (boot camp/Tabata/spin/P90X) 5 - 6 days/week. Healthy.....for the last 3 days, I have found when my heart rate is moderate to high, I am seeing a spot (kidney shaped) in one eye. When I close my eyes, I can still see the shadow of the shape if that makes sense.....it ultimately goes away - 5 - 10 minutes later, then does not reappear....any thoughts? Thanks so much!