What Causes Twitching In Eyelids?

I have an eyelid twitch that started in one but now has become a problem with the other eye. Enough for me to think my eyes are having some kind of tremor. however, nobody sees it. I do like my cocktails so on the days those I think it would be caused from that. I am 48 years old. not active but weight is within a good bmi. when I go for an annual check up...... then insist on what?