The possibility is that Joey has been 'becoming diabetic' for months or even years, without you or your vet necessarily being aware of it. As the diabetes
developed, so secondary symptoms would have developed, including cataract.
Blind dogs can manage very well, but obviously it is better to have the cataracts removed if finance permits. Dogs blind from birth fare better than dogs that become blind later in life. You already have an understanding about not moving furniture, etc.