I've been using all types of mac computers, phones and tablets since around 2005 with absolutely no issues. I'm a technology trainer who teaches software and stares at PCs, Macs, and HDTV's all day. In 2017 I purchased an iMac Pro and from the moment the apple logo over black came on during boot up, it immediately hurt by eyes. I put the machine aside for about a year. I then decided to play with it again and went through numerous trouble shooting phases including SwitchResX, Ram and other PRAM resets, FLux, ect. When rebooting, one time it came up and the problem was completely gone. So something I did took it out of the mode that was causing my severe eye strain. Problem is, I don't know what I did to fix it because I was trying multiple solutions one after another. And it was well over a year ago. Worked with it no issues at all for 1.5 years. Recently went into the Display settings, held OPTION down so when I hit the SCALED button it would reveal exact resolution setting, and it INSTANTLY change the display settings to bring the EYE PAIN back immediately. The only thing I saw change was that the fonts got crisper (more detailed) and the color saturation increased. The size of the fonts did not change. And I can't get it to go away again.
In 2019 I purchased a 13" MacBook Pro. No eye issues at all. Then, after causing the iMac Pro display to return to causing eye strain, the 2019 MacBook pro also starting causing me eye strain issues. I didn't change any settings on it. Someone suggested because I've got my accounts syncing to the cloud, the display settings from the iMac Pro migrated to the 2019 MacBook Pro. I don't know if I buy that or not. I did upgrade the OS on both machines months ago and there was no eye strain related to that. I worked on them both successfully for months after. My gut tells me that there was a configuration in the older OS that I was able to manipulate to remove the issue causing the eye strain, and that config was retained even though I upgraded the OS. But when I went into the iMac's Display setings and hit OPTION + SCALE, it caused it to overide the previous OS config and click into the newest OS display settings. I can't prove this, but it feels like this might be it. I can't explain why the MacBook Pro would all of a sudden start causing me problems.
By the way, I'm also putting both the iMac Pro and MacBook Pro through non-Retina HD-only external monitors to eliminate the possibility of it being a problem with my looking at the built-in Retina displays on those machines. Didn't help.
All of a sudden, my iPhone 12 Pro Max is also causing me eye strain. Never did that before.
I suspect spending all day working on these machines is causing eye fatigue which is making it more difficult for me to look at any computer screens. Even my HDTV has slowly started causing eye strain, but not as severe. I have found that turning all the displays complete black and white has halved the eye strain. Doesn't entirely eliminate it, but it does allow me to not have to pop Extra Strength Tylenols for headaches.
Eye doctor says nothing is wrong with my eyes. I have been using readers for computer work for years, just for focus assistance. We're now trying some prescription glasses with various blue light and other options to see if this will help at all. I will get them later this week and report back.
To see if this was only Mac-related, I picked up an inexpensive Windows Laptop and worked on that for a week. It was alot less eye strain, but still there.