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.
In most cases, you won't even notice when the twitch has stopped. More severe contractions, where the eyelid completely closes, are possible. These can be caused by irritation of the surface of the eye (cornea) or the membranes lining the eyelids (conjunctiva). Sometimes, the reason your eyelid is twitching cannot be found. This form of eyelid twitching lasts much longer and is often very uncomfortable. It can also cause your eyelids to close completely. Repeated uncontrollable twitching or spasms of your eyelid (most often the upper lid)