I seem to have variations, I have a bad one at Christmas when I saw my parents (a trigger), I remember my emotional focus (I can only describe it as this) becoming smaller and smaller like the aperture on a camera. I could see everything but I could only focus on specific areas and not everything as a whole. I sat with some of my family who surrounded me, preventing my parents getting close, and I could only concentrate on my cousin's mouth as she talked to me. I think this was just to keep conscious, as I thought I may totally black out.
The other day I saw my mother shopping so I decided just to leave the store, as I left I felt again I was blacking out but not enough to totally become overwhelming like the previous Christmas. This time is was more on a whole and I was more aware of my surroundings. I drove home as was explaining to my daughter what was happening and I knew what was happening but this was more subtle although unsettling.
This is the first time I have had to explain this and it is quite difficult.