this sounds like a twitching? rather than spasms?

Twitching muscles in your age group, can be due to poor dietary intake
of magnesium and essential fatty acids.
In fact a drug company was going to market a product specifically for this.
Magnesium also helps..most people do not eat enough magnesium containing foods, and instead drink alot of caffeine containing liquids. Caffeine will set off spasms too.

So try to do some dietary changes...if EFAs and Magnesium do not work, then check with a doctor. You may have simple allergies that irritate the eye lids.
If you are female, don't use cosmetics for a while, see if that helps.

to read:
EFAs in the diet and foods with them:
http://neurotalk.psychcentral.com/showthread.php?t=6092

magnesium supplements and dietary sources:
http://neurotalk.psychcentral.com/showthread.php?t=1138

These are the most likely causes for someone your age.