I have posted somewhere else about my experience with this, but cannot remember where that was. To make a long story short, I had several tests done, including a brain scan, because it was driving me crazy. The neurologist told me there was nothing wrong, and that it was caused by stress. I got a second and even third opinion, all the same. It was very difficult for me to believe that it was stress, although I was very much entrenched in severe stress at the time, because the twitching didn't seem to happen at the exact same time that the stress SEEMED to occur. I was told by all the docs that it did not have to occur at the same time, and that my body was trying to let me know in a physical way because I was not listening to the emotional clues. Sometime after that, my life changed drastically, the stress was gone, and so was the eye twitch. It has never returned to this day. If you cannot find any other explanation for the twitching, maybe you might want to consider this as a possible cause?
Deb