My senior cockapoo has PRA, not cataracts, but he is a blind dog that we've done a lot of stuff for (we got the GSD for him, actually).
So obviously the vet is the first step. Treatment is usually surgery or eye drops/ointments with medications. They may ask you if you even want to do surgery given their age, and that is your decision. They'll give you those details and info on how safe it all is, how effective, and give you their recommendations. I was told when we were still diagnosing his PRA that they wanted to do medications as much as possible for treatments because of Brodie's age, and I was pretty much like "if we think it'll save future trouble, take the eyes, his blood work is good". Turns out it was PRA and he can just blissfully slide into full blindness with no discomfort, no treatments necessary.
While he has safety sunglasses, I actually got a hat for my boy because day blindness was a really big issue we saw first and foremost. He couldn't see ANYTHING in the harsh sun, but a hat gave him at least outlines of things around him. The sunglasses are TOO dark and he couldn't see at all in them when he had a LITTLE bit with the hat.
I do give him saline eye washes weekly to make sure he doesn't have any dirt or grime build up and cause infection.
If you find that their eyesight is getting affected, stick to a single route for a walk. Makes it way easier for them to feel confident doing it, and it makes them still have that routine they crave.
If your dog isn't already good with eye drops, do the saline wash now and get them ready to receive them. It won't hurt them but it'll get them ready to receive medication. You can also use something like coconut oil to massage around (not in or close to) the eyes to emulate ointments.
That's all I can really think of for now but if I think of anything else, I'll add it!