thorpee I had a similar experience. I was fine with some beta versions of Big Sur and Safari 14, but then when it was released it really bothered my eyes. Monterey was the same. If I use Catalina and Safari 13 I'm fine. Something changed with graphics in Mac OS 11 and newer. Unfortunately, the Apple Silicon machines can't run versions older than Big Sur, so I can't really test this on newer machines. But my 2017 MBP I can literally boot back and forth between Catalina and Big Sur and back and my eyes are fine, then they hurt, and then fine again. If I upgrade Safari to 14 or 15 on Catalina my eyes hurt, even though the rest of the apps and OS are OK. Its so weird.