I agree it could be eyesight, it could also be seperation anxiety, a good trainer could help if its seperation anxiety - your vet might know a good trainer (positive training only though, dogs are like humans - they dont react well to getting punished all the time)

Imagine this: a creature much bigger than you puts something round your neck then says words you dont understand, every time you get it wrong what they want, they punish you for it, compared with positive-training, which the person shows you what they want so you learn what everything means