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.
The most common known causes of eye twitch include fatigue, stress, anxiety, and excessive caffeine intake. Eyelid twitch may appear in response to irritation caused by smoke, dust, or a foreign body in the eye. Allergies and infections may also cause irritation that leads to twitching. Eyelid twitch is seen in primary congenital glaucoma.