Awww. Poor chickens. Have you googled Mumble the Blind Chicken, yet? I think she has a facebook page. She was born with no eyes but is thriving and happy as far as I know.
Sometimes, they make her little special "prosthetic" eyes:
I am sad to say that my special chick passed away.
I think she might have had a mental issue as well, she did a lot of head bobbing and pecking at the air above the ground, without actually picking anything up.