The upper eyelid of my left eye has has been twitching for a few days. I googled to find out why this started suddenly, and whether I need to worry about it. Here’s what I found:

Called myokymia in doctor lingo, these rippling muscle contractions in an eyelid can be triggered by:

• Stress
• Tiredness
• Eye strain
• Caffeine
• Alcohol
• Dry eyes
• Nutritional imbalances
• Allergies

OK, one question answered, and now I have a new one: Given the potential causes, why have my eyelids not twitched every day of my adult life?