I have high blood pressure and mvp.. And afew other health problems.. But one thing I have an occasional problem with, if I just sit for a little while,( now this is not always), but after I stand up for afew moments, I be gin to feel a pressure build up in my head, and it follows my pulse , as it progresses, my hearing will begin to become like a roar, and eventually , my sight goes as well. Once this went on for so long. I was at a meeting and someone had introduced me to a gentleman, as I was introduced my vision completely went black, but I was still aware of what was going on around me, I just stuck out my hand to shake his , my vision began to clear up and the poor guy had the strangest look on his face and quickly turned and walked away!I always feel alittle tired after this happens. Now I try to sit down or slow my walking till it passes.Any ideas what this could be ? Lily