I can't remember exactly how old or blind he was supposed to be but yes. According to Julius Norwich's History of Byzantium, the Doge helped lead the assault that finally breached the top of the sea walls, leading to the success of the campaign. Hopefully, someone with a better idea can clarify as I do not have the book in front of me, but he was quite old...probably not completely blind. Remember, being blind is a spectrum, you can be blind and still be able to kind of see, which from my recollection, is what the Doge was. Blind and old, but not completely blind.