A simplified guide on how to test whether PWM affects you
.1. Make sure your phone has low frequency PWM, using a pencil test. You can use your finger instead of a pencil.
Video that illustrates what you can see with a pencil test
Set your phone to your usual brightness level and go to a room where there are no flickering lamps. Wave your pencil in the air: you should see 2 pencils around the edges and between them there is a blurred, even trail of movement.
Now wave a pencil in front of the screen: if there is a low frequency PWM, you will see a lot of pencils instead of two. The lower the screen brightness, the stronger the PWM will be.
Check PWM on a white or light image on the screen. PWM may not be visible on dark images and there will be no PWM on black image.
If you didn't see the PWM as a result of this experiment, but your phone uses PWM to adjusts the brightness or other purposes, then its flickering is too frequent for most human eyes. According to IEEE 1789-2015, frequencies above 400 Hz are safe for most people.
Your eyes may be hypersensitive, but without special equipment it would be hard to check the PWM level that is right for you.
.2. Remove the PWM on your phone (this step can be done only on Android)
2.1. PWM is either absent at 100% brightness on most phone models, or becomes imperceptible. Set it to 100% brightness and see if it becomes easier for you. In order not to burden the eyes with brightness, for the purity of the experiment, conduct it in a well-lit place or on the street.
If it helps you, the cause of your problem is PWM.
2.2. Turn on dc dimming on your phone. Or remove PWM using Oled Saver or any other program that mimics dc dimming. It works like this: at 100% brightness, the program applies a black filter to the image to get the visual brightness of the screen you need. The picture quality will drop, but the picture will be created without the help of PWM technology.
After turning on the Oled Saver, do a pencil test to make sure the PWM is gone.
If it helped you and there is no pain in the eyes, the cause of the problem is PWM.
If it became easier for you, but partially, it can indicate that besides PWM, something else is bothering you.
Or you are facing with a response to high-frequency PWM and you need additional equipment to measure it.
If there is no difference, the cause of your pain is not PWM.
.3. Test phones without PWM
Important: in this experiment, you are changing not one parameter - PWM, but a whole bunch of parameters. You pick up another phone, which may have hundreds of differences from your phone.
Therefore, you will not be able to pinpoint the exact cause of the pain or eye strain.
Use noteboockcheck.net, where there is a table of PWM measurements for all phones. Notice, that measurements are available not for every phone, only for models starting from 2016-2017. Select models for the test. These can be phones with an IPS screen, or phones with OLED (Amoled, Super Amoled ec.) screen with a PWM frequency of 500 and higher. It is advisable to look at least at 5-6 different phones in order to narrow the range of causes of your pain. Two IPS phones from different years and manufacturers can be as different as night and day. If you only test one IPS phone, you might come up with a wrong conclusion.
Watch phones in dim lighting.
If it helps, PWM may be the cause of your pain. Or it may not be, testing different phones is not enough to pinpoint exact source with 100% probability.