I'm sorry for the diagnosis. Are you sure it's not the thickening that is a normal part of aging in senior dogs? See Your Dog’s Eyes (3) | My Dog Space
That blue-ish senior thickening is nothing to be worried about--it doesn't rob them of sight.
If it's really a cataract (which blocks light and will rob them of sight), I strongly recommend a visit to a vet ophthalmologist. I have a dog with double cataracts (totally blind, and has been for years). He has to see his specialist twice a year, as the cataracts change and require monitoring, and sometimes intervention. General practice vets are good for spotting the issue, but I really think a referral to a specialist is needed beyond that.
The specialist will do a much more thorough eye exam, with special instrumentation that likely can't be found at a regular vet clinic. Mine charges around $150 for that exam, and it takes a good hour. They'll get a really good look into the eyes, and come up with a plan for going forward.
Here's why you want a specialist involved:
1. Sometimes cataracts are
operable to save the vision, if caught early enough. This is sophisticated surgery, done only by specialists as far as I know (it's several thousand dollars, per eye).
2. Dogs with cataracts often need to be on anti-inflammatory or steroidal RX eye drops to prevent glaucoma (a very painful disease that require removing
the entire eye). An eye specialist can assess this risk, and figure out what, if anything is needed.
3. There are nutrition supplements for eyes that are likely to be prescribed or recommended directly from the eye specialist. Ocu-Glo is one I've seen dispensed in the clinic, for example. They can also talk through with you what to avoid -- the specialists tend to know the research on nutrition and eyes well and are a good sounding board for you.
This should help you find a vet eye specialist - the American College of Veterinary Ophthalmologists:
Veterinarians & Public
Please don't despair! Even if your dog is going blind, it will be okay. They adjust much better than humans do. My blind one leads a full, normal life and isn't a pity case -- he goes to training classes, goes hiking and enjoys outdoor adventures, swims, romps with other dogs, chases squirrels, and acts like a totally normal dog. People often don't even realize he's blind when they watch him. We've learned how to give him a normal life safely, and if you ever hit this point with your dog, I can send you a ton of info by PM.
Oh -- and get him a pair of super-cool Doggles!!! You now have an excuse to have a dog that wears shades.