Just once. I've had to have laser surgery on my left eye to patch up a hole somewhere and prevent impending retinal detachment.
I wasn't able to sit still, considering that there was a glass piece pushing on my eyeball and an awful burning sensation in the back of my eye. And moving my eyes around meant that the surgery went on longer to patch up holes created by heating up the wrong place, meaning that the pain increased, meaning that I moved my eye more, meaning that they had more holes to patch up... you can see where this is going.
Worst part is, retinal detachment can still happen despite a surgery. I think I'm at a greater risk than normal because he couldn't really patch up all the problems that happened because of how much my eye was twitching.