I don't believe there is anything you can put in - there is something questionable sold in pet shops made for dogs or cats but I don't think it can be safely used for ferrets. Also I have a 5 year old who has been blind with glaucoma since he was 3. He lives a good life, it's hard to remember he is even blind. But with cataracts they can be painful. I would concentrate on pain relief if needed. Laryssa [Posted in FML 6276]