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.
Eye twitching, or myokymia, is an involuntary eyelid muscle contraction that usually affects the lower eyelid. The exact cause of eye twitching is unknown. A twitch sometimes develops during times of increased stress. Eye twitching has also been associated with high caffeine intake, fatigue or excessive squinting.