LCD means Liquid crystal display, its just how a flat screen works, I work in an office in a bunker for 2 days 2 nights and then 4 days off, 12 hour shifts always at a PC Screen.
Every hour however i take a 10 minute break to go upstairs for a smoke, my eyes are fine and I dont tend to get head aches either. (thing is I cant say the same about lung cancer in a few years time)
My point is though if you take a regular break (5 - 10 mins per hour), allow your eyes to look at distant objects (even just looking out of the window) you will find less strain on your eyes and headaches will become less persistant.