The problem is definitely related with the light emission. I know this because spending little time at front of a new display not only causes me eye strain but also a high skin pain. Refresh rate has nothing to do with it. It is related with the backlight type.
It happens to me with all new displays (TV, monitors, phones, notebooks and LED bulbs). I can use devices with old kind of backlights 24hs a day without any problem. Specially devices with CCFL or old LED backlights. The only exception I detected is with some big CCFL monitors with more nits (cd per m2) that also cause me problems.
The confirmation to it is that with old Samsung LED TV, that was the first device that hurts me, I solve this problem by lowering the backlight option to the minimum. After that I could use it as normal.
It seems related with the maximum nits of the backlight that is always on, and with his light spectrum. Lowering the bright doesn't solve the problem, only the backlight. It seems that the dangerous light emitted by the backlight couldn't be completely filtered by the bright or contrast of the LCD that is at front of the light source.
Displays with PWM is on at the maximum power of the backlight for a fraction of time, and is a very intense and harmful light. If I put the brightness at 100%, apps like oled saver doesn't solve the problem at all, at least not enough.