Hello everyone, I will try to help you but since I'm not a doctor I will share my opinion and what I've read during biology classes and on the internet.
I will give you some recommendations and I strongly insist to check a doctor (at least your family doctor) if your problem still occurs. Well, I don't know for sure but I do believe that the problem could be "eyestrain" and that is caused by lack of sleep and / or stress. These factors are causing spastic twitching of the eyelids.
Usually, eyestrain has manifestations as you've described up there: when throbbing occurs behind the eye or when you have a sudden eye ache. As I said it can be caused by two factors: lack of sleep (which I assume that everything is clear here) and stress caused to your eyes. That includes: keeping your eyes focused at the same distance for long time, having to change focus often (when you read from notes and then address them to an audience) or working under bright lights with high contrast. Moreover, you might stress you eyes if your work has you staring at more or less the same thing all day (staring at a computer screen all day for example). All this is very simple to explain: your eyes are controlled by muscles and when you're having this muscles to exercise too hard for too much time or when you are tensed in one position for too long also can be tiresome.
So, here are few recommendations: try to relax your eyes a few minutes of every hour or you may let your eyes to focus at a different distance. Moreover, if you drink a lot of caffeine I would suggest you to cut it down for at least awhile. As I mentioned above, I recommend you to visit a doctor if relaxation and stopping bad habits won't help you. If you notice that eye problems are giving you troubles working or especially when driving (I guess I don't need to explain this) you have to visit a doctor IMMEDIATELY! Good luck everyone and be healthy!