Watch our report from ITV News Anglia's Hannah Pettifer
A rescue dog from Cambridgeshire has been called a medical mystery after having been born blind but his condition went undetected for the past seven years.
It came as a huge surprise to his owner Jane Downes who lives in Waterbeach especially she says as Dave walks around puddles and streetlamps, chases other dogs, and has always easily found his way around the house.
Jane adopted him from a rescue centre in February last year, but it wasn't until he stumbled over a step that someone suggested he may be blind.
Later tests revealed he'd been sightless from birth.
Dave even managed to negotiate around our camera while we were filming him.
Ophthalmologist Dr David Williams from Cambridge University's Vet School was asked to examine Dave and admits it's a conundrum