Brief Answer:
Most common causes listed below

Detailed Answer:
Hello and welcome.

Thank you for writing in.

There can be many causes for involuntary twitching of the eye. For your reference I shall list all the possible causes for you. They are:
-Stress
-Fatigue
-Excessive caffeine, alcohol, tobacco use
-Neurological conditions (eg. Parkinsons disease, Tourettes syndrome, bells palsy, etc.)
-Nutrient deficiencies
-Blepharospasm (condition causing involuntary closing of the eyelids)
-Organic problems with the eye (eg. infections, dry eyes, increased sensitivity to light, etc.)
-Lack of sleep
and a few others.

But the above are the most common causes for an involuntary twitching of the eye. I hope you found my response helpful. Please feel free to write back to me for any further clarifications.

Best wishes.

---