1 Touch Response: The keys on a digital piano or keyboard can be weighted (similar to those of a traditional piano), touch sensitive (unweighted but still sound loud when struck hard), or neither.
In very rare instances, eyelid twitching can indicate a more serious condition, like the beginning stages of multiple sclerosis or a lesion on the brain stem. Those conditions typically begin with a host of symptoms, and in this circumstance the eyelid twitch soon moves to the facial muscles, as well.
Types of eye twitching. Minor eyelid twitch also can be caused by irritation of the surface of the eye ( cornea) or the membranes lining the eyelids (conjunctiva). Sometimes the cause of minor eyelid twitch cannot be identified. In almost all cases it is painless and harmless.