my 14 year old son just told me about an episode of getting up from a sitting position and having his vision go to black and dizziness and the vision return. He was walking away from couch and remembers taking hold of staircase banister and then falling to his butt and next falling completely and hitting head on wooden floor. He was home alone at the time. After this he has shared with me many episodes of this eye vision issue and that it s been occurring for months. I had no idea until his fall. Is this a blood pressure thing, or dehydration as I hear others speak about similar symptoms?