Damn that beats the torture practises of the inquistion although on a second those were painful too. Though I don't understand why they atleast wouldn't wear a blindfold in the portrait. Weren't people with mutilations and scars considered to be devils in human disguises back then or something like that?
At least in The Alexiad blinded people are treated as just people that have lost their eyes as a punishment for being on the losing side. In fact, the book mentions one blinded ex-rebel accompanying Alexios I to his campaigns against Scythians (the folks in Romania).
Quoting the book, "'I will tell you this, my Emperor: if you cross the Haimos, you will appreciate the fastest horses.' Someone asked him what he meant. 'For when you flee,' he replied, 'all of you.' This Bryennios, although he had lost his eyes because of a revolution, was recognized to be a foremost authority and expert on strategy and tactics."
You revolted against the wrong person and you lost your eyes, you were by tradition considered incapable of being Emperor because Emperorship was mandated by God and God is perfect and a mutilated person can't thus be Emperor but besides that they were just normal people who often were allowed to live out their lives in monasteries.