Do your eyes ever "spasm"?

I'm not sure how to describe this. My eyes do this thing sometimes when I'm focusing on something close-up, they'll involuntarily dart side to side a couple of times really fast. I have no control over it, don't know when it's going to happen, and they move faster than I could consciously move them. The only word I can think to describe it is a "spasm". I tried to ask my husband if it happens to him and he had no idea what I was talking about. Anyone else experienced this?