Absence of light

Last night, during the beer chilling session in Eckywoobee, I've experienced in the state of being dark for around 3-4 minutes twice. How could this happened? Alright, here the story goes..

I was drinking and chilling with friends during that time, after around an hour, I felt like going to the toilet, when i stood up, my eyes suddenly seeing everything in a very bright condition and about 10 seconds later, it was slowly getting darker and darker until I couldn't see anything but only darkness. I was like blinded on that time, honestly to you, it was kinda scary. I didn't know what happened to my eyes and what's the reason causing that. Even until now, I'm still curious about it. I stood by a side and made some rest, after around 3-4 minutes later, I felt my vision were coming back, I was be able to see everything after that. I got back to my seat and continue chilling, but after around 15 minutes later, the problem came back. This time it's even longer than the first time, it was around 5 minutes. So I do the same thing of what I did, with some rest, my vision came back again. This is the first time I been into this kind of condition, completely darkness.