Ensuring your frog is always hydrated is a good start, just plop the frog in the bowl if you think it hasn't had water in the a while a sick WTF is a frog that doesn't move much so keep a eye on it's activeness at night, also ensure that the e the tank is clean to stop any infections, I am not a specialist in frogs but the eye can be a very delicate thing so I wouldn't advise home treating this, maybe a vet is your only option. Hope this helps.