so a german friend of mine... back in his mid 20's had just moved into a new apartment and didn't have much in it just yet, it was winter and the previous tenants had left behind their old space heater. My friend had a date with a girl that evening but had a few hours to kill till them so he wanted to read and keep warm by the heater. Two hours or so later he got up to go pick up his date and along the way to her house started feeling really weird, and his vision was getting a little blurry and by the time he reached her front door he completely lost his sight and went blind while he was trying to find her door buzzer. His date opened the door to find him freaking out and not able to see so she quickly took him to the emergency room where he was examined and bandaged up and his date took him back to his house... so much for a first date right?
I'll tell you why he lost he felt so weird and lost his sight... later.