I'm definately not an expert, but it seems to me that if the cataracts aren't bothering him and he's happy and otherwise healthy, it may not be of much benefit to try to correct the problem. Much of a dog's world is created around smell, so he's probably just adapted to not seeing well. But definately talk to a vet you trust ... they should be honest with you. It could be the surgery is very easy on the dog and would be worth a try.

FWIW, I had a 20-year-old cat who went blind three years before she died. She also went deaf at about the same time. She just went right about her business, and right up until the end, was perfectly happy. Animals are pretty amazing in their ability to just keep chugging along.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)