Why does my right eyelid keep twitching?

Twitching eyelid : Twitching eyelids called "myokymia" in one eye one lid is most likely a sign for eye strain of the kind occurs with need for glasses correction or adjustment, general fatigue, eye dryness, etc. Simultaneous upper and lower lid spastic closure with or with out facial spasm might be more serious condition as would be bilateral lid closures. See an eye doc.