Seriously, I have one and bothe eyes are completely clouded over. A sign is if it is a shoaling fish (like my bala shark) and it does not shoal with the other fish.
I have also noticed that my blind Bala grows at an excruciatingly slow rate. He's put on around 1 to 1.5" in the last year. The one we bought at the same time has put on around 3.5 to 4".