I posted a little while back how YouTube changed "something" in their video player which rendered it unusable for me. I experimented with writing a little desktop application that would play YouTube videos in a standalone player, VLC stopped supporting YouTube a while back, but I found PotPlayer still supports it. After mucking around with all the settings, I found that watching YouTube videos with the following settings results in zero eye strain
Saturation: 25%
Codec: avc
Resolution: 360p
FPS: 30
Just thought I would share if anyone else had this issue.