I want to leave some of my personal experience. Before I know any screen knowledge, my first tablet is the iPad air 1st generation. I can use it to read pdfs for several hours without any discomfort to my eyes. Later, after the iPad pro 2020 came out, I bought an 11-inch one. I don't know why. I read the pdf on the 11-inch iPad pro 2020. After ten minutes, I felt very uncomfortable for my eyes. I put the pdf on my MacBook pro. I obviously feel more comfortable with my eyes on the screen, I don't understand why, I started searching for related user feedback and screen knowledge, and found the difference between OLED and LED, but I checked, iPad pro is also the screen of LED, I am very confused. Later, I discovered the dimming method, and when I saw this website, I immediately understood the root cause of everything. I ordered iPad air 4, and I can read the pdf for several hours. PWM really has a great impact on my eyes.
[My eyesight is very good, the physical examination is 1.5 1.5, which is the bottom line of the eye chart, the above is for reference