I posted this in another thread, but I thought of sharing it here too.
I have tried many different phones like Samsung, LG, Huawei, Lenovo and all of them give me eye strain. I have purchased phones, only to get eye strain, and had to sell it again.
So far, the only phones that I can use without eye strain are phones that uses the Super LCD3 display (i.e. HTC One M7, One Max, HTC One M8, M9 and M9+). These are the phones that I can use and look at the screen for hours (e.g. watching youtube or movies on my phone) without any eye strain whatsoever.
Other display technology like SuperAmoled (Samsung phones), IPS (LG, Huawei, Lenovo etc) all give me eye strain. My wife is using Samsung Note 5, and I cant look at her phone for more than 2 minutes. The PWM in Samsung phones are quite bad. Her previous Samsung phones (S4) also cause me eye strain. Some newer HTC phones are starting to use IPS like the HTC Desire Eye, HTC E9+ etc, these also cause me eye strain, so not all HTC phones are okay, only their flagship series (M8, M9, M9+).
Right now I am using HTC One M9+ Supreme Camera edition, which I had to import from Hong Kong. This is the "best" phone that I can use right now. "Best" as in a phone with the largest screen that I can use without causing me eye strain. It is 5.2 inch, which is slightly smaller than I would like, but at least the camera is much better than my old phone (HTC One Max).
I also tried LG V10 for a couple of weeks. Great phone, does not seem to have PWM (at least based on simple my video camera test), but I do get eye strain using it from time to time. It is not like immediate eye strain as soon as I look at it, which is typical for a PWM-related eye strain), but this is more like a discomfort on the eyes, you feel something that is causing discomfort on your eyes (not sure how to describe it exactly)....and after looking it the screen for some time, it gets painful. So I am going to sell my LG V10 soon.