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 is causes blepharospasm. There are many causes of eye twitching. The common ones are alcohol, caffeine, fatigue, lack of sleep, physical exertion, smoking, stress, and irritation to the eye or eyelid.