JJ, You can have a Schirmer's test to see if your eyes are dry. It's pretty standard here in the US.

http://www.nlm.nih.gov/medlineplus/e...cle/003501.htm

Eyes can also be dry from not enough acetylcholine, just as too much can cause tearing.

Twitching eyelids can be from MG, a nerve issue, electrolyte imbalance, eyestrain, and a lot of other causes.

Annie