I loved that bug. To the point that I actually spent a (probably unnecessary) number of hours QC'ing it to try to figure out what was causing it. I didn't manage to figure out that it was the blinding check that was a problem, but I did discover that if you basically murdered all the people in the Byzantine empire, or you elimited the cultures that allowed blinding people, your game perf would go way up.

So I made a little personal mod that immediately castrated (if there was something to castrate) and blinded all characters of the Byzantine empire on game start, and it seemed to solve the problem.