What works for you, what do you use now without problems?

AGI Do you have perfect vision?

No, I have astigmatism with -4 and -5 spherical value.

AGI Have you ever had any thought it might be your eyes to cause digital eyestrain, and got checked?

Yes, I got it checked and it did not get better with new glasses. When I am away from my screen I do not have issues. So it is certainly the computer.

AGI How about LED and fluorescent lamps?

Had to remove all LED bulbs in our flat. That already calmed down my neural system a lot! Have halogen bulbs now. They last way longer than incandescent ones. No problems with fluorescent lamps as I know.

AGI Uh, I bought an open box iPhone 6s a week ago on eBay

Sorry, my bad. I have an iPhone 6 Plus, not 6s. My wife has a 6s. However that got worse after she upgraded from iOS10 to iOS12. So if the phone still runs iOS10 and you can bear it I would refrain from upgrading it...

deepflame So if the phone still runs iOS10 and you can bear it I would refrain from upgrading it...

Thanks on the tip! I will see when it arrives. It is an "open box" item. I hope they do not update the OS before shipping!

deepflame No problems with fluorescent lamps as I know.

Since I changed job, I have developed eyelid and face muscle twitching. After quite some time, I figured out it is mostly caused by the ceiling fluorescent lamps. I do have fluorescent lamps in the apartment I rent, and I have no problem. I tried to look at the emission spectra and wavelength-wise I cannot find a clear difference although the "bad" lamps look of a warmer color. Funnily, I can see by the naked eye the bulb in my kitchen flicker and it does not bother me. I am clueless.

diop Have you tried Windows 8/8,1?

No, but this is a good point. I always disliked the new start screen but just found out that it is possible to bring back the "old" start menu from Windows 7. Good to know to have this option.

diop Are you affected by temporal dithering?

Well, I am not sure what kind of dithering it is (seems there is also spatial dithering) but I am highly affected by pixel flickering. Also DLP projectors give me strain after a while.

diop Nvidia driver settings

Please let me know if you need anything else.
I need to add that I have disabled "ClearType". Not sure if this is off by default. Turning it on makes the screen unusable again.

diop I can see these Quadro K420 cards are very affordable on the used market

Yes, I started with the Quadro NVS 295 for 4 EUR on Ebay and gave this another shot and have to say it is really worth it. Of course I cannot guarantee that yours will be the same because of revision differences. However I have hopes as @JTL had a similar experience with his Quadro K4000 ( https://ledstrain.org/d/337-nvidia-quadro-k4000 ). So it seems to me that the Kepler Quadro cards may generally be good (?).

diop It really is becoming a joke.

Yeah, I know what you mean. My wife is also already fed up with all this "buying new screens and returning them". There are still 7 or so standing around there that I need to sell or dispose. Based on the positive response from some people it is definitely worth it and to never lose hope!

deepflame Thank you for your input, your input is very interesting. You said S-PVA is better than IPS panel. Did you experience Eizo IPS panel monitor? Is there any chance that just Eizo monitor is good for eye strain?

deepflame Which iOS version do you run on your 6S? In my experience it got worse with iOS 11 (10 was really good)

Sorry for jumping it. I just got my 6s with iOS 10 and had three bad days following 20 minute usage. Sticky eyes and a very annoying neck tension causing enormous difficulties to work with laptop and PCs which are normally fine. It could be that my eyes are not in the best shape to tell what is causing what, but it is quite obvious that the 6s is not for me. I also asked the office who lent me the iPhone last year. They could not tell me its OS version but it was a 6 and not a 6s. So it is not the 6s worked earlier and does not now, as I initially speculated.

Lauda89 I tryed a lot of monitor flicker free that killed my eyes.

What are your symptoms? How long do they take to develop? In particular, do you get immediate neck tension? How long does it take to recover?
I remember the iPhone X gave problems to many, and on forums fingers were pointed at the 240 Hz PWM. If you can stand that, it looks like PWM is not your problem?
However, I do not recall all members' stories and issues. I guess you know that a flicker-free monitor can give troubles if connected to "bad" hardware, do not you? That is something I was not aware of until I found this forum an year ago, so I am not the expert for sure.

I can use most computers but I can't find a smartphone that does not make huge damages. I owned only one so far, which worked beautifully until an year ago. I had no chance but to re-sell the other three phones I recently bought. Impossible to use them.
I too do not think PWM is my problem. In the recent past I used devices at very, very low brightness, and could watch as long as I wanted. I am clueless. And demoralized. I can only say, the newer the technology, the worse.