長い時間パソコン使った後は、まぶたがぴくぴく痙攣しますって英語でなんて言うの？

When you want to explain that your eyes twitch after using the computer for a long time, you can say:
Extended time at the computer makes my eyes twitch.
Extended - In this case it means a long period of time. A long time, a lengthy time.
At the computer - This is the most common way of saying that you are sitting in front of the computer or that you are using the computer.
Makes - causes
My eyes twitch - This means to make them blink repeatedly.

Spending a long time at the computer can also:
It makes my eyes tired.
It makes my vision blurred.

You can also say:
My eyes are twitching from spending so much time at the computer.
Spending so much time - Using a lot of time to do something.

I hope that helps!

Tic = an habitual spasmodic contraction of the muscles, most often in the face.
synonyms: twitch, spasm, jerk, convulsion, contraction, tremor, tremble
"He had a nervous tic around his left eye."
You may also describe a tic as being 'an inadvertent twitch.'

"After working on the computer for a long time, my eye starts to twitch." explains that after staring at a computer screen for a while you get a twitch in your eye.

When you want to explain that your eyes feel weird when you spend too much time in front of the computer, then you can say:
-My eyes twitch when I use a computer for a long time
-My eyes become sore when I use a computer for lengthy/extended periods

It is very common to get eyestrain resulting from sitting in front of, and looking at the computer screen for a long time. This can also result in the twitching on the eyes. However, if you are working on an urgent project, you may not stop just because your eyes are twitching. So, if you do get this type of sensation at any given point in time, you may say to your work colleague:
My eyes are twitching because of sitting in front of the computer for too long.
or
Due to eye strain as a result of looking at my computer screen for too long, my eyes are twitching.