I went to a friends house and smoked weed I n his back yard. After we had smoked a joint together, I got up out of the seat and got a head rush. My vision started to fade 'til I cud only c a small part of my environment. I do sometimes get a head rush when I get up but im not sure y. The head rush I got this time afta smoking lasted for ages, I took some water & eventually my vision came back. My legs felt wobbly. When I tried getting back up again I got the same head rush but this time my vision completely blacked out and my head felt very hot. My vision was restored about 30 seconds later but not completely.I eventually made it to my friends living room and crashed out for about an hour.occasionally I got up 2 see how my vision was and It still was messed up a little. Eg blurry lines.About 1 hour later I was fine. i had eaten well that day. Its about the 6th time I have smoked weed & it hasnt happened before. I need 2 find out why this happened to me and what i can do about it.