They are called OcluVet, and there is little data on the success rate,
especially for cats, since cataracts are so uncommon in cats. Here's the
website:http://www.ocluvet.com/

They aren't cheap, it looks like around $130 for 2 months worth (using
in 2 eyes; 4 months treating 1 eye).

Even though they're expensive, I might give them a try after
researching, provided they don't seem like complete snake oil. The
thinking is that the drops might slow down progress, not eliminate the
cataract entirely.

That's really pricey for what appears to be antioxidants and vitamins?
I hadn't heard of these before. I'm not sure they would help in our
situation, since one cataract (in our cat's 'bad' eye) has already
matured and stabilized. I'd be interested to see any research/etc. you
might find.