I have the same problem , i just got my iphone 12 and last week and i had sever eye strain and headache , no matter what setup you. I had to return it and stick with my iphone XR. The strange part when i used my cousin Galaxy S20 i never got a headache or eye strain. I was wondering if the refresh rate has anything to do with this ???? samsung refresh rate 120 and Apple 60... some insight about the refresh rate and impact on our eyes is highly appreciated.

I had the same issue as fernandho.

I got so ill looking at the Iphone 12 I had to return it.  I went back to my Iphone 8. 

I've had issues with various devices, but nothing as immediate and pronounced as the new iphone. 

Can you do the same test for iPhone 12 Pro Max and possibly iPhone 12 Mini to observe the differences in PWM implementation between the iPhone 12 lineup?

I had no idea about this but I used an iphone 12 mini for one week and it caused me really serious eye strain to the point I felt dizzy and my sight was so blurry I couldn't read the newspaper nor use the computer. I am back to my iphone SE and my sight recovered. I supposed some people are more sensitive than others. The interesting thing is that I don't even use hte phone that much. What I feel disappointed is that apple did not provide me any kind of help or support. They just said there is nothing they could do. Kind of a shame.

Is it worse than Samsung phones? I have no issues with them, while iPhone XS (my only oled experience so far with oled on Apple devices) was a nightmare...I'd like to get a 12 pro max, but I am worried about this

Are you aware if it used at 100%?