I have had my iPhone 11(64gb) for over 3 years and am dying to get a new phone. I had to return iPhone 11pro when I had constant headaches and eye strain for a week, since then I had opportunities to use 12 Mini, 13 and 13pro max on and of but never for a really long period of time. I didn't develop any immediate headaches from those usage but my eyes always felt funny. I cannot say they made me feel bad, just not as comfortable as looking at the iPhone 11 screen for me.
Today I was at the Apple store playing with iPhone 14pro for about 20 minutes, again, no headaches but my eyes still felt a little funny. I don't know if it's due to PWM or I'm just adjusting to OLED screen. I feel slightly hopeful and maybe will try to order an iPhone 14pro this year(looked at 14 as well, but I really like the look of pro version better). I love how the silver version looks, way better than the silver regular 14. I'm hoping once I'm adjusted to the new phone, it won't be an issue. Good luck everyone, please keep sharing your experiences with the new phones.