Welcome to BYC. Please go to your original post about your blind duck; there are suggestions on it.
I have Muscovy femae who is blind in one eye, and it looks perfectly normal and a female Runner who is blind in one eye, and you can definitely tell it's cloudy
Look how cute I wish it was light enough in their brooder room at night for the camera to not be infrared black and white haha! Just a puddle of babies!