Hi,

Please get your dog checked by your vet, your theory on her eyesight is a possibility.
Sadly, however, I fear there is a rather more sinister reason for your bitch behaving in this way. She sounds as though she is a nervous dog. This is a trait that can not be trained out of her and is likely to be more pronounced as she ages. You will have to be aware at all times of her disposition and careful of the situations you introduce her to. Socialisation may improve her slightly but I'm afraid the trait is in her genes and will always be there. Fear biting is always a risk with such a dog, especially with children. Try to ignore her behaviour in the house and keep her under close control when out or you have visitors.
Your dogs quality of life has to be under question as she is a constant state of anxiety, but only you know how bad her problem is.
I hope I'm wrong and it must be stressed that without meeting the dog I can not be certain.