Does anyone know what might be happening? I'm 15, and for two years, I've been having this problem. Two or three times a day, I lose my vision for about half a minute. It's usually only when I get up too quickly, but the severity of what I think is related varies. Whenever it happens, my vision goes, but about once a week I'll suddenly lose my vision for no apparent reason (while walking around, usually) and I hear a faint, static-like sound. My legs start to shake, and I collapse, losing my ability to control myself, and I shake violently for 10-20 seconds before all of it just clears up and I'm fine again. Other times during the week, I'll get to the point of collapsing, but I don't shake. My doctor has suggested dehydration, but even after I had gotten the recommended amount of water every day for two months, there was barely any improvement at all.