Sitting in front of my computer for too long has caused me eyestrain and headaches for the past couple of years and I've just kind of accepted it. But tonight I was researching the problem and came across this article which schooled me on a couple of things: 
 
http://www.flatpanelshd.com/focus.php?subaction=showfull&id=1362457985
 
Basically what it's saying is that modern LED's use pulse width modulation to control the brightness of your screen. When you reduce the brightness from 100% (which most people do because most monitors are ridiculously bright), it achieves the lower brightness by turning the LEDs off and on again in a pulse. Obviously the shorter the pulse length, the lower the brightness. But this introduces an imperceptible flicker which causes eyestrain and headaches. 
 
So what's the solution? 100% brightness is way too bright, especially at night. Well I already use Flux on my desktop and laptop - it warms and dims the colors on screen so that you're not burning your eyeballs out with too much blue light at night, thus helping you relax and fall asleep easier. It really works. I have found that when I turn my monitor brightness up to 100% and then turn Flux's nighttime setting to its minimum value (2700K), I can achieve a sort of happy medium. The screen is still a little too bright for my taste, but Flux dims and warms it considerably to the point where it's not blinding me. I did this a couple of hours ago and I'm happily used to it already. The screen is tolerable and best of all the monitor itself is at 100% brightness so no PWM dimming going on. It remains to be seen if this reduces or stops my eyestrain, I'm quite hopeful though. 

I have to check this out. Super helpful tip! Thank you.

A happy medium?  Isn't that what your psychic is after they get paid? 

craigb
A happy medium?  Isn't that what your psychic is after they get paid? 

Why wouldn't she be happy about being paid before I paid her? She is, after all, a psychic. 

Good point.

A couple of weeks ago I read about night time phone use and it said also about software that dims and filters blue light from the phone to make it better suited for night time use. Now I use an app called Twilight in my Android and it is easier to fall asleep if I use my phone in bed.

So thanks to you sharke, I installed that Flux on my LED 21" monitors late last night and the color sat went from blue/white to yellow and a lot less bright. I reset the monitors settings to default and let Flux do its thing and I like it.
It changes the hue/brightness of the monitors based on the time of day.  In the day, they are bright and at night they change. I only tested last night but think this will help my eyes and also help me get some sleep.  I hear the melatonin in our bodies gets whacked when looking at bright LED monitors and that's one of the chemicals that we need for better sleep. 
Ramble....
But I really appreciate your bringing a possible solution to the forum.  
 
ZZZZZzzzzzzzz
 

I like to keep my monitor brightness between 120% and 140% (which, naturally, is 20-40% better). 

Rimshot
So thanks to you sharke, I installed that Flux on my LED 21" monitors late last night and the color sat went from blue/white to yellow and a lot less bright. I reset the monitors settings to default and let Flux do its thing and I like it.
It changes the hue/brightness of the monitors based on the time of day.  In the day, they are bright and at night they change. I only tested last night but think this will help my eyes and also help me get some sleep.  I hear the melatonin in our bodies gets whacked when looking at bright LED monitors and that's one of the chemicals that we need for better sleep. 
Ramble....
But I really appreciate your bringing a possible solution to the forum.  
 
ZZZZZzzzzzzzz
 

So did you set your monitor to 100% brightness as well? I think that's vital to stop or reduce the flicker. What I discovered last night is that Flux has hot keys to reduce the brightness of the screen via software (Alt + Page Up/Down) so that you can enjoy a dimmer display without having to turn the actual monitor brightness down. 
 
I've used Flux for almost 2 years now and I don't know how I could live without it. I had a horrible time sleeping before that. The warmer colors look a bit weird at first but you quickly get used to them. For giggles I sometimes turn the Flux slider all the way up to see what it used to look like. That harsh blue light burns right through your eyeballs, it's horrible. 

Fluorescents, which most of us work under all day (unless you're lucky enough to have an outdoor job when it's -40), do the same thing. Only difference is you're not staring directly at them @ close range.