I am so saddened by the hard time people have given the OP here. Talk about beating someone when they're down.
Our old girl is diabetic and completely blind - she has been for a year. She's 15 years old.
Every day we feed and inject her with insulin, 12 hours apart.
Walks have to be carefully managed (they can decrease or increase blood glucose levels).
We test her blood at home to reduce her trips to the vet. We make sure we're with her to feed her and inject her on time, every single day, early mornings and late evenings, to keep her as healthy as we can.
She has cancer. She had a tumour removed in September and luckily bounced back from a major operation despite a heart murmur.
She has the very odd accident. Usually a wee on the floor or on her sofa from high blood sugar.
But she negotiates the garden with skill that you couldn't imagine from an animal who has no sight at all.
We've adapted games to play with her that rely on her other senses.
She loves her walks and is completely confident despite losing her sight. She is still happy, active and as healthy as she can be despite everything.
She is my best friend and I love the bones of her. I know she loves me and she's still very, very happy and contented.
But if dementia and/or extreme incontinence should set in, which it might, then we would do the right thing by her and us.
Just like ImportSave is thinking about with her dog.
To make this decision isn't because the dog is an inconvenience.
A dog that's incontinent to this degree at such an age does not have a good life, and neither does their owner.
I'm so sorry you're going through this ImportSave and for some of the horrible responses you've had.
Take him to a different vet to see if there is something simple that's been missed. And after that, if you feel it's time to say goodbye to him, then do that for him with a clear conscience.