Hi, I'm Shin.
I have used MacBook air 2010 for almost 10 years, which has been really good with no eyestrain at all.
I bought MacBook pro-2018 a few months ago and encountered serious eyestrain, headaches, and dizziness.
It was so weird that even though the screen was really bright and sharp, I felt that I cannot focus well on the screen it was like seeing a screen with wrong glasses. Few days later, after seeing the screen for just a few seconds, I could feel the strain in my eyes right away and headache began. More severe problem was that the symptom lasted a few days after even though I wasn't looking at the laptop screen. It was so frustrating. I have changed the resolution, fonts, applied anti-glare films, changed the brightness of the screen to low to highest (PWM issue?) nothing helped. However, an interesting thing was when I used Windows 10 with Bootcamp, my eyes were fine. When I turned on windows 10 with parallels, also my eyes were fine. Only on MacOS, I had the problem. When I plugged into the external monitor. It was better but still, there was eyestrain. I think it's not the problem of laptop LED itself, but the way MAC OS (Mohave) projects images or fonts on the screen.
I discussed it with my family and friends, but the responses were "You're being too sensitive". However, the symptoms are real. I didn't sell or changed my Macbook pro, but using as a windows machine. However, I wonder if there's anyone has a similar issue. Maybe downgrading Mohave to other OSX version might help?