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.
Experts believe that the eyelid twitching of blepharospasm is caused by the misfiring of certain cells in one area of the brain. Eyelid twitches may be aggravated by having dry eyes. They may also be worsened by stress, lack of sleep, caffeine, and harsh light conditions.