If Mat is actually the man in the middle (and not the man on the right), it seems as if he is wearing a red bandage around his head, which might extend over his left eye. We know from one of Egwene's Dreams that Mat will place his left eye on a balance scale. If this left eye is the connection to the Finn, it makes sense that Mat has to give it up/cut it out before he and the others enter the Tower of Ghenjei to avoid warning the Finn. This would explain the bandage.