Since my issues with mac, I moved over to Win 10. There were no issues at all. Just this am 1 update got pushed on my PC - which was the Intel HD 620 - Graphics driver update.
My new driver version is 188.8.131.5286. Since this am - I have the same eye strain I used to have with the mac, which makes me wonder if this eye strain has always been about the graphics driver?
I have 2 Win 10 machines, both got the update - same result.