In the comments, viewers have shared their own stories of ageing pets, many admitting they'd never noticed the change until it happened. Videos like this often hit hardest because they're so personal.

It is widely believed dogs see in black and white. But recent studies have proven otherwise for what colors dogs can see.

The attractive brown colour is thanks to Eumelanin ... (Also read: How long might your dog live? New study calculates life expectancy for different breeds) Be it the friendly and intelligent ...

My dog's favourite colour is purple and she won't play with a toy that's not purple." Another wondered: "Can they see brown? My dog's favourite toy is brown." According to information about dogs ...

A neglected dog dumped outside a rescue centre 'changed colour' after being given a much-needed bath. The animal's matted fur was first believed to be black and dark brown. A good groom ...

"But whether or not the dog's sensations are missing red and green, or if their brains assign colors differently, is unclear." Furthermore, like people with colorblindness, dogs may use other cues ...